Since security exploits can now be found by spending tokens, open source is MORE valuable because open source libraries can share that auditing budget while closed source software has to find all the exploits themselves in private.
> If Mythos continues to find exploits so long as you keep throwing money at it, security is reduced to a brutally simple equation: to harden a system you need to spend more tokens discovering exploits than attackers will spend exploiting them.
An app like Cal.com can be vibe coded in a few evenings with a Chrome MCP server pointed to their website to figure out all the nooks and crannys. The moat of Cal.com is not the code, it's the users who don't want to migrate.
The real answer is they are likely having a hard time converting people to paid plans
"AI slop is rapidly destroying the WWW, most of the content is becoming more and more low-quality and difficult to tell if its true or hallucinated. Pre-AI web content is now more like the golden-standard in terms of correctness, browsing the Internet Archive is much better. This will only cause content to go behind pay-walls, allot of open-source projects will be closed source not only because of the increased work maintainers have to do to not only review but also audit patches for potential AI hallucinations but also because their work is being used to train LLMs and re-licensed to proprietary."
This conclusion makes more sense to me, but maybe I'm too naive.
The media momentum of this threat really came with Mythos, which was like 2 or 3 weeks ago? That seems like a fairly short time to pivot your core principles like that. It sounds to me like they wanted to do this for other business related reasons, but now found an excuse they can sell to the public.
> to harden a system you need to spend more tokens discovering exploits than attackers will spend exploiting them.
That can't be right, can it? Given stable software, the relative attack surface keeps shrinking. Mythos does not produce exploits. Should be defenders advantage, token wise, no?
So long as that OSS keeps accumulating features, there isn't quite the equilibrium you're imagining. If you can pin to a stable version, which continues to audited, you're fine. But if the rest of the world moves on to newer versions of the software, you'll have to as well, unless you want to own the burden of hardening older versions.
It also means that you need to extract enough value to cover the cost of said tokens, or reduce the economic benefit of finding exploits.
Reducing economic benefit largely comes down to reducing distribution (breadth) and reducing system privilege (depth).
One way to reduce distribution is to, raise the price.
Another is to make a worse product.
Naturally, less valuable software is not a desirable outcome. So either you reduce the cost of keeping open (by making closed), or increase the price to cover the cost of keeping open (which, again, also decreases distribution).
The economics of software are going to massively reconfigure in the coming years, open source most of all.
I suspect we'll see more 'open spec' software, with actual source generated on-demand (or near to it) by models. Then all the security and governance will happen at the model layer.
> I suspect we'll see more 'open spec' software, with actual source generated on-demand (or near to it) by models. Then all the security and governance will happen at the model layer.
So each time you roll the dice you gamble on getting a fresh set of 0-days? I don't get why anyone would want this.
You already do this with human-authored code, just slowly.
Project model capabilities out a few years. Even if you only assume linear improvement at some point your risk-adjusted outcome lines cross each other and this becomes the preferred way of authoring code - code nobody but you ever sees.
Most enterprises already HATE adopting open source. They only do it because the economic benefit of free reuse has traditionally outweighed the risks.
If you need a parallel: we already do this today for JIT compilers. Everything is just getting pushed down a layer.
This seems similar to the lesson learned for cryptographic libraries where open source libraries vetted by experts become the most trusted.
Your average open source library isn’t going to get that scrutiny, though. It seems like it will result in consolidation around a few popular libraries in each category?
An important difference between SaaS offerings and open source libraries is that the latter have not liability. They can much more easily afford exhibiting vulnerabilities until those are fixed.
I expect we're about to find that it's a lot easier to convince a company to spend money running an AI security scan of their dependencies and sharing the results with the maintainers than it is to have them give those maintainers money directly.
(I just hope they can learn to verify the exploits are valid before sharing them!)
This seems kind of crazy. If LLMs are so stunningly good at finding vulnerabilities in code, then shouldn't the solution be to run an LLM against your code after you commit, and before you release it? Then you basically have pentesting harnesses all to yourself before going public. If an LLM can't find any flaws, then you are good to release that code.
A few years ago, I invoked Linus's Law in a classroom, and I was roundly debunked. Isn't it a shame that it's basically been fulfilled now with LLMs?
After a release, attackers have effectively infinite time to throw an LLM against every line of your code - an LLM that only gets smarter and cheaper to run as time passes. In order to feel secure you’d need to do all the work you’d imagine an attacker would ever do, for every single release you ship.
Attackers only need LLMs to be good at randomly finding one vulnerability, whereas service providers need them to be good at finding all such vulnerabilities.
LLMs really are stunningly good at finding vulnerabilities in code, which is why, with closed-source code, you can and probably will use them to make your code as secure as possible.
But you won't keep the doors open for others to use them against it.
So it is, unfortunately, understandable in a way...
I'm not a security expert but can't close source applications be vulnerable and exploited too? I feel like using close source as a defense is just giving you a false sense of security.
Finding a vulnerability in a black box is drastically different from finding one in a white box. This isn’t about whether there is a vulnerability or not, but about the likelihood of it being found.
It's not a "project" though; the business Cal.com Inc raised that VC money. Their open source repo did not raise the money.
Did they ever promise to keep their codebase FOSS forever, in a way that differs from what they're already doing over at cal.diy? If not, I don't see why it would be reasonable to expect them to spend a huge amount of money re-scanning on every single commit/deploy in order to keep their non-"DIY" product open source.
I mean, you should definitely have _some_ level of audit by LLMs before you ship, as part of the general PR process.
But you might need thousands of sessions to uncover some vulnerabilities, and you don’t want to stop shipping changes because the security checks are taking hours to run
It's entirely possible to address all the LLM-found issues and get an "all green" response, and have an attacker still find issues that your LLM did not. Either they used a different model, a different prompt, or spent more money than you did.
It's not a symmetric game, either. On defense, you have to get lucky every time - the attacker only has to get lucky once.
Hey cal.com, as a potential customer, you have just lost me.
Open source is set to profit from improved transparency in the SSDLC. With closed source, you will have to trust the software vendor instead.
I'm not sure I agree with Drew Breunig, however. The number of bugs isn't infinite. Once we have models that are capable enough and scan the source code with them at regular intervals, the likelihood of remaining bugs that can be exploited goes way down.
Yeah, I don't buy it. If they don't want these security reports, ignore them and continue your path. Blaming AI is just an excuse to close source. If you don't want AI to learn from your code, too late. Add genetic algorithms and fuzzing into AI and it can iterate and learn a billion times faster, no need to learn for humans.
Security through obscurity is only problematic if that is the only, or a primary, layer of defense. As an incremental layer of deterrence or delay, it is an absolutely valid tactic. (Note, not commenting on whether that is the rationale here.)
Going closed source is making the branch secret/private, not making it obscure. Obscurity would be zipping up the open source code (without a password) and leaving it online. Obscurity is just called taking additional steps to recover the information. Your passwords are not obscure strings of characters, they are secrets.
If there is a self-hosted version at all, then the compiled form is out there to be analysed. While compilation and other forms of code transformation that may occur are not 1->1, trivially reversed, operations, they are much closer to bad password security (symmetric encryption or worse) then good (proper hashing with salting/peppering/etc). Heck, depending on the languages/frameworks/other used the code may be hardly compiled or otherwise transformed at all in its distributed form. Tools to aid decompiling and such have existed for practically as long as their forward processes have, so I would say this is still obscurity rather than any higher form of protection.
Even if the back-end is never fully distributed any front-end code obviously has to be, and even if that contains minimal logic, perhaps little more than navigation & validation to avoid excess UA/server round-trip latency, the inputs & outputs are still easily open to investigation (by humans, humans with tools, or more fully automated methods) so by closing source you've only protected yourself from a small subset of vulnerability discovering techniques.
This is all especially true if your system was recently more completely open, unless a complete clean-room rewrite is happening in conjunction with this change.
Right, but those capabilities are available to you as well. Granted the remediation effort will take longer but...you're going to do that for any existing issues _anyway_ right?
I understand why this is a tempting thing to do in a "STOP THE PRESSES" manner where you take a breather and fix any existing issues that snuck through. I don't yet understand why when you reach steady-state, you wouldn't rely on the same tooling in a proactive manner to prevent issues from being shipped.
And if you say "yeah, that's obv the plan," well then I don't understand what going closed-source _now_ actually accomplishes with the horses already out of the barn.
Or internalize the cost if they all decide the hassle of maintaining an open source project is not worth it any more.
I'm not aiming this reply at you specific, but it's the general dynamic of this crisis. The real answer is for the foundational model providers to give this money. But instead, at least one seems to care more about acquiring critical open source companies.
We should openly talk about this - the existing open source model is being killed by LLMs, and there is no clear replacement.
I don't think this really helps that much. Your neighbor could ask an LLM to decompile your binaries, and then run security analysis on the results.
If the tool correctly says you've got security issues, trying to hide them won't work. You still have the security issues and someone is going to find them.
If I understand correctly, their primary product is SaaS, and their non-DIY self-host edition is an enterprise product. So your neighbor wouldn't have access to the binaries to begin with.
It only takes 20 minutes and $200 to hack a closed source one too though. LLMs are ludicrously good at using reverse engineering tools and having source available to inspect just makes it slightly more convenient.
Very true, but that is still a meaningfully higher cost at scale. If, as people are postulating post-Mythos, security comes down to which side spends more tokens, it is a valid strategy to impose asymmetric costs on the attacker.
Couldn't you just spend those $100 on claude code credits yourself and make sure you're not shipping insecure software? Security by obscurity is not the correct model (IMO)
> neighbors son 15 mins and $100 claude code credits
Is that true? Didn't the Mythos release say they spent $20k? I'm also skeptical of Anthropic here doing essentially what amounts to "vague posting" in an attempt scare everyone and drive up their value before IPO.
We did consider arguments in both directions (e.g. easier to recreate the code, agents can understand better how it works), but I honestly think the security argument goes for open source: the OSS projects will get more scrutiny faster, which means bugs won't linger around.
Time will tell, I am in the open source camp, though.
This certainly makes me feel better about the project I started a few months ago to replace my Cal.com instance with a smaller, simpler self-hosted tool
I am beyond convinced at this point that you either run an Open Source Project with a small revenue company (single digit millions) or run a software company that does more than 10M ARR at the least and be closed source. I know there are exceptions but most open source Software companies are providing code with heavy restrictions or teaser features and gate keep everything in their "ee/enterprise" version etc.
I know plenty of security researchers who exclusively use Claude Code and other tools for blackbox testing against sites they don’t have the source code for. It seems like shutting down the entire product is the only safe decision here!
The real threat is not security but bad actors copying your code and calling it theirs.
IMHO, open source will continue to exist and it will be successful but the existence of AI is deterrent for most. Lets be honest, in recent times the only reason startups went open source first was to build a community and build organic growth engine powered by early adaptors. Now this is no longer viable and in fact it is simply helping competitors. So why do it then?
The only open source that will remain will be the real open source projects that are true to the ethos.
I agree with you that AI's disruption of attribution is a much bigger problem, but it's also worth recognizing that not everyone has this same motivation. It mostly affects copyleft open source licenses.
Attribution isn't required for permissive many open source licenses. Dependencies with those licenses will oftentimes end up inside closed source software. Even if there isn't FOSS in the closed-source software, basically everyone's threat model includes (or should include) "OpenSSL CVE". On that basis, I doubt Cal is accomplishing as much as they hope to by going closed source.
In my advisory job founders always raise the question about open sourcing within the first hour of meeting me. They think that open sourcing product means transparency and developer trust which helps with early adoption. Every single founder I talked to brings up open source as a market penetration method to drive the initial adoption.
I always say to just stop with the virtue signaling led sales technique.
I despise the "we are like the market leader of our niche but open source" angle. Developer as a buyer and as a community these days in my opinion do not care about open source anymore. There is no long term value to that. The moment a product gets traction the open source elements is a constant mild headache as open source product means that they have no intellectual copyright on the core aspect of the product and it is hard to raise money or sell the company. And whenever a product gets traction they will take any excuse to make it close source again. With an open source product they are just coasting on brand. Regardless of what your personal opinion is, this has been largely true for most for-profit business.
Open source is largely is nothing more then a branding concept for a company who is backed by investors.
Today, it's easy to (publicly) evaluate the ability of LLMs to find bugs in open source codebases, because you don't need to ask permission. But this doesn't actually tell us the negative statement, which is that an LLM won't just as effectively find bugs in closed codebases, including through black-box testing, reverse engineering, etc.
If the null hypothesis is that LLMs are good at finding bugs, full stop, then it's unclear to me that going closed actually does much to stop your adversary (particularly as a service operator).
Juxtapose this with the fact that many HNers will decry strong copyleft FOSS licenses as not being truly "open source" - the reality is that closed source software is still full of open-source non-copyleft dependencies. Unless you're rolling your own encryption and TCP stack, being closed source will not be the easy solution that many imagine it to be.
- You know, Lindsay, as a software engineering consultant, I have advised a number of companies to explore closing their source, where the codebase remains largely unchanged but secure through obscurity.
- Well, did it work for those companies?
- No, it never does. I mean, these companies somehow delude themselves into thinking it might, but... but it might work for us.
Monumentally dumb given their codebase is already public and the type of security issues that exist in software are usually found in the oldest code. But also, and more importantly, cal.com launched coss.com last year, open source is (ostensibly) their DNA. How could they do a complete 180 on something so fundamental and think that wouldn’t worry customers, much more so than their codebase being public? I cannot even begin to understand this. Surely there must be more to the story?
Coss.com reads like a half assed pivot if you look at it with today's news. It's clear cal.com isn't making enough money and going closed source is yet another attempt to fix that.
Oh wow the coss.com thing makes this so much worse. Making such an aggressive and public commitment to open source to then turn around and do something like this is a pretty rough look.
TIL I learned about yet another calendar application I don't need. Someone should setup their openclaw to just write a new todo/calendar app each week; they'll be billionaires by the end of the year.
I hate how this sounds...but this reads to me "we lack the confidence in our code security so we're closing the source code to conceal vulnerabilities which may exist."
This is some truly exceptionally clownish attention seeking nonsense. The rationale here is complete nonsense, they just wanted to put "because AI" after announcing their completely self-serving decision. If AI cyber offense is such a concern, recognize your role as a company handling truckloads of highly sensitive information and actually fix your security culture instead of just obscuring it.
I mean it's not complete nonsense, but yeah, doing it for security reasons sounds like BS. I actually thought this was going to be about how AI makes it super easy for someone to steal all their code and fold it into their own competing project. I've seen a few open source projects get sideswiped by this, AI is pretty good at copying code (and obfuscating the fact that it was copied). I suspect that's the real reason but it doesn't sound as good. So they went with this half-truth.
Risk tolerance and emotional capacity differs from one individual to another, while I may disagree with the decision I am able to respect the decision.
That said, I think it’s important to try and recognize where things are from multiple angles rather than bucket things from your filter bubble alone, fear sells and we need to stop buying into it.
This is the future now that AI is here. Publishing is going to be dead, look at the tea leaves, how many engineers are claiming they don’t use package managers anymore and just generate dependencies? 5 years and no one will be making an argument for open source or blogging.
> if AI can be pointed and find vulnerabilities then do it yourself before publishing the code
At your cost.
Every time you push. (or if not that, at least every time there is a new version that you call a release)
Including every time a dependency updates, unless you pin specific versions.
I assume (caveat: I've not looked into the costs) many projects can't justify that.
Though I don't disagree with you that this looks like a commercial decision with “LLM based bug finders could find all our bad code” as an excuse. The lack of confidence in their own code while open does not instil confidence that it'll be secure enough to trust now closed.
For-profit companies using open-source software should bear that cost - that's my position.
I believe than N companies using an open source project and contributing back would make this burden smaller than one company using the same closed-source project.
Open-source supporters don't have a sustainable answer to the fact that AI models can easily find N-day vulnerabilities extremely quickly and swamp maintainers with issues and bug-reports left hanging for days.
Unfortunately, this is where it is going and the open-source software supporters did not for-see the downsides of open source maintenance in the age of AI especially for businesses with "open-core" products.
Might as well close-source them to slow the attackers (with LLMs) down. Even SQLite has closed-sourced their tests which is another good idea.
The tools are available to everyone. It's becoming easier for hackers to attack you at the same speed that it's becoming easier for you to harden your systems. When everyone gains the same advantage at the same time, nothing has really changed.
It makes me think of how great chess engines have affected competitive chess over the last few years. Sure, the ceiling for Elo ratings at the top levels has gone up, but it's still a fair game because everyone has access to the new tools. High-level players aren't necessarily spending more time on prep than they were before; they're just getting more value out of the hours they do spend.
I agree it's a shit tactic, but one thing I can say for those running software businesses is that it's not an equivalent linear increase on both sides. It's asymmetric, because # of both attackers and the amount of attack surface (exposed 3rd party dependencies, for example) is near infinite, with no opportunity cost for failure by the bad actors (hackers). However a single failure can bring down a company, particularly when they may be hosting sensitive user data that could ruin their customers' businesses or lives.
I think Cal are making the wrong call, and abandoning their principles. But it isn't fair to say the game is accelerating in a proportionate way.
Ultimately, he concludes that while in the short run the game defines the players' actions, an environment that makes cooperation too risky naturally forces participants to stop cooperating to protect themselves from being "exploited" (this bit is around 34:39 - 34:46)
Sure, I can see that to a degree. And there definitely is a bit of chaos during the transition period as everyone scrambles to figure out what the landscape looks like now. I could understand if they decided to temporarily do less-frequent code releases, or maybe release their code on a delay or something, while they wait for the dust to settle. But I don't think permanently ending open source development is the right move.
Agreed! There must be a way to maintain the principles and benefits of open-source; the alternative, which is that all software becomes a black box, is antithetical to the same security that that choice supposedly aims to achieve.
I think companies make decisions like this from a tactics level, not realizing that by doing so they are not only alienating their customers but misunderstanding the basic (often unconscious or unspoken) social contract upon which their very existence is predicated.
Calendly already existed. Cal came along and said, ok, but what if the code were out in the open -- auditable, self-hostable. Then you wouldn't have to worry about lock-in, security, privacy, etc, in the same way. Now they are removing that entire aspect of their value prop. It may be the only thing that caused a good portion of their customers to adopt in the first place.
Drew Breunig published a very relevant piece yesterday that came to the opposite conclusion: https://www.dbreunig.com/2026/04/14/cybersecurity-is-proof-o...
Since security exploits can now be found by spending tokens, open source is MORE valuable because open source libraries can share that auditing budget while closed source software has to find all the exploits themselves in private.
> If Mythos continues to find exploits so long as you keep throwing money at it, security is reduced to a brutally simple equation: to harden a system you need to spend more tokens discovering exploits than attackers will spend exploiting them.
Thanks - I've re-upped* that one here: Cybersecurity looks like proof of work now - https://news.ycombinator.com/item?id=47769089 (no comments yet)
* a la https://news.ycombinator.com/item?id=26998308
I have a feeling the real reason is them trying to avoid someone using AI to copyright-wash their product, they're just using security as the excuse.
An app like Cal.com can be vibe coded in a few evenings with a Chrome MCP server pointed to their website to figure out all the nooks and crannys. The moat of Cal.com is not the code, it's the users who don't want to migrate.
The real answer is they are likely having a hard time converting people to paid plans
> The moat of Cal.com is not the code, it's the users who don't want to migrate.
That's a very weak moat unless you have something else like the friction of network dependence similar to a social network.
Exactly this! Classic open source bait and switch.
Called this 9 months ago https://news.ycombinator.com/item?id=44559840
"AI slop is rapidly destroying the WWW, most of the content is becoming more and more low-quality and difficult to tell if its true or hallucinated. Pre-AI web content is now more like the golden-standard in terms of correctness, browsing the Internet Archive is much better. This will only cause content to go behind pay-walls, allot of open-source projects will be closed source not only because of the increased work maintainers have to do to not only review but also audit patches for potential AI hallucinations but also because their work is being used to train LLMs and re-licensed to proprietary."
This conclusion makes more sense to me, but maybe I'm too naive.
The media momentum of this threat really came with Mythos, which was like 2 or 3 weeks ago? That seems like a fairly short time to pivot your core principles like that. It sounds to me like they wanted to do this for other business related reasons, but now found an excuse they can sell to the public.
(I might be very wrong here)
> to harden a system you need to spend more tokens discovering exploits than attackers will spend exploiting them.
That can't be right, can it? Given stable software, the relative attack surface keeps shrinking. Mythos does not produce exploits. Should be defenders advantage, token wise, no?
> Mythos does not produce exploits.
AI in general will, don't worry. "Move fast and break things" makes more exploits than "move steadily and fix things" does.
It’s the classic asymmetric warfare problem:
Defenders have to find all the holes in all their systems, while attackers just need to find one hole in one system.
So long as that OSS keeps accumulating features, there isn't quite the equilibrium you're imagining. If you can pin to a stable version, which continues to audited, you're fine. But if the rest of the world moves on to newer versions of the software, you'll have to as well, unless you want to own the burden of hardening older versions.
This is an economically sound conclusion.
It also means that you need to extract enough value to cover the cost of said tokens, or reduce the economic benefit of finding exploits.
Reducing economic benefit largely comes down to reducing distribution (breadth) and reducing system privilege (depth).
One way to reduce distribution is to, raise the price.
Another is to make a worse product.
Naturally, less valuable software is not a desirable outcome. So either you reduce the cost of keeping open (by making closed), or increase the price to cover the cost of keeping open (which, again, also decreases distribution).
The economics of software are going to massively reconfigure in the coming years, open source most of all.
I suspect we'll see more 'open spec' software, with actual source generated on-demand (or near to it) by models. Then all the security and governance will happen at the model layer.
> I suspect we'll see more 'open spec' software, with actual source generated on-demand (or near to it) by models. Then all the security and governance will happen at the model layer.
So each time you roll the dice you gamble on getting a fresh set of 0-days? I don't get why anyone would want this.
You already do this with human-authored code, just slowly.
Project model capabilities out a few years. Even if you only assume linear improvement at some point your risk-adjusted outcome lines cross each other and this becomes the preferred way of authoring code - code nobody but you ever sees.
Most enterprises already HATE adopting open source. They only do it because the economic benefit of free reuse has traditionally outweighed the risks.
If you need a parallel: we already do this today for JIT compilers. Everything is just getting pushed down a layer.
This seems similar to the lesson learned for cryptographic libraries where open source libraries vetted by experts become the most trusted.
Your average open source library isn’t going to get that scrutiny, though. It seems like it will result in consolidation around a few popular libraries in each category?
An important difference between SaaS offerings and open source libraries is that the latter have not liability. They can much more easily afford exhibiting vulnerabilities until those are fixed.
How may open source libraries have auditing budgets?
I expect we're about to find that it's a lot easier to convince a company to spend money running an AI security scan of their dependencies and sharing the results with the maintainers than it is to have them give those maintainers money directly.
(I just hope they can learn to verify the exploits are valid before sharing them!)
Their commercial users have auditing budgets.
Does your ideal world have an easy path to citizenship?
I might like to live there.
Security should be a non issue in the age of AI now that auditing is cheaper than ever.
I'd give them more credits if they use the AI slop unmaintainability argument.
This seems kind of crazy. If LLMs are so stunningly good at finding vulnerabilities in code, then shouldn't the solution be to run an LLM against your code after you commit, and before you release it? Then you basically have pentesting harnesses all to yourself before going public. If an LLM can't find any flaws, then you are good to release that code.
A few years ago, I invoked Linus's Law in a classroom, and I was roundly debunked. Isn't it a shame that it's basically been fulfilled now with LLMs?
https://en.wikipedia.org/wiki/Linus%27s_law
After a release, attackers have effectively infinite time to throw an LLM against every line of your code - an LLM that only gets smarter and cheaper to run as time passes. In order to feel secure you’d need to do all the work you’d imagine an attacker would ever do, for every single release you ship.
Attackers only need LLMs to be good at randomly finding one vulnerability, whereas service providers need them to be good at finding all such vulnerabilities.
LLMs really are stunningly good at finding vulnerabilities in code, which is why, with closed-source code, you can and probably will use them to make your code as secure as possible.
But you won't keep the doors open for others to use them against it.
So it is, unfortunately, understandable in a way...
I'm not a security expert but can't close source applications be vulnerable and exploited too? I feel like using close source as a defense is just giving you a false sense of security.
Finding a vulnerability in a black box is drastically different from finding one in a white box. This isn’t about whether there is a vulnerability or not, but about the likelihood of it being found.
Delaying attacks is a form of valid security.
That’s a non-trivial cost for commonly severely underfunded open source projects
Cal.com is not a severely underfunded project, it raised around $32M of VC money.
It's not a "project" though; the business Cal.com Inc raised that VC money. Their open source repo did not raise the money.
Did they ever promise to keep their codebase FOSS forever, in a way that differs from what they're already doing over at cal.diy? If not, I don't see why it would be reasonable to expect them to spend a huge amount of money re-scanning on every single commit/deploy in order to keep their non-"DIY" product open source.
I mean, you should definitely have _some_ level of audit by LLMs before you ship, as part of the general PR process.
But you might need thousands of sessions to uncover some vulnerabilities, and you don’t want to stop shipping changes because the security checks are taking hours to run
It's entirely possible to address all the LLM-found issues and get an "all green" response, and have an attacker still find issues that your LLM did not. Either they used a different model, a different prompt, or spent more money than you did.
It's not a symmetric game, either. On defense, you have to get lucky every time - the attacker only has to get lucky once.
> It's not a symmetric game, either. On defense, you have to get lucky every time - the attacker only has to get lucky once.
This! I love OSS but this argument seems to get overlooked in most of the comments here.
Hey cal.com, as a potential customer, you have just lost me. Open source is set to profit from improved transparency in the SSDLC. With closed source, you will have to trust the software vendor instead.
I'm not sure I agree with Drew Breunig, however. The number of bugs isn't infinite. Once we have models that are capable enough and scan the source code with them at regular intervals, the likelihood of remaining bugs that can be exploited goes way down.
Related ongoing threads:
Open Source Isn't Dead - https://news.ycombinator.com/item?id=47780712
Cybersecurity looks like proof of work now - https://news.ycombinator.com/item?id=47769089
This is a weird knee-jerk reaction. I feel like this is more a business decision than a security decision.
I feel like with AI, self-hosting software reliably is becoming easier so the incentives to pay for a hosted service of an OSS project are going down.
Yeah, I don't buy it. If they don't want these security reports, ignore them and continue your path. Blaming AI is just an excuse to close source. If you don't want AI to learn from your code, too late. Add genetic algorithms and fuzzing into AI and it can iterate and learn a billion times faster, no need to learn for humans.
AI is certainly getting a lot of milage as an excuse for doing bad things.
Wanna sack a load of staff? - AI
Wanna cut your consumer products division? - AI
Wanna take away the source? - AI
Their product is getting commoditized: https://workspace.google.com/resources/appointment-schedulin...
I always felt it was a matter of time before Google took notice.
It has always been odd to me they didn’t have this functionality years ago. It’s been requested for a long long time
I get the mentality but it feels very much like security through obscurity. When did we decide that that was the correct model?
Security through obscurity is only problematic if that is the only, or a primary, layer of defense. As an incremental layer of deterrence or delay, it is an absolutely valid tactic. (Note, not commenting on whether that is the rationale here.)
This is not security via obscurity; it is reducing your attack surface as much as possible.
Reducing your attack surface as much as possible via obscurity.
Going closed source is making the branch secret/private, not making it obscure. Obscurity would be zipping up the open source code (without a password) and leaving it online. Obscurity is just called taking additional steps to recover the information. Your passwords are not obscure strings of characters, they are secrets.
If there is a self-hosted version at all, then the compiled form is out there to be analysed. While compilation and other forms of code transformation that may occur are not 1->1, trivially reversed, operations, they are much closer to bad password security (symmetric encryption or worse) then good (proper hashing with salting/peppering/etc). Heck, depending on the languages/frameworks/other used the code may be hardly compiled or otherwise transformed at all in its distributed form. Tools to aid decompiling and such have existed for practically as long as their forward processes have, so I would say this is still obscurity rather than any higher form of protection.
Even if the back-end is never fully distributed any front-end code obviously has to be, and even if that contains minimal logic, perhaps little more than navigation & validation to avoid excess UA/server round-trip latency, the inputs & outputs are still easily open to investigation (by humans, humans with tools, or more fully automated methods) so by closing source you've only protected yourself from a small subset of vulnerability discovering techniques.
This is all especially true if your system was recently more completely open, unless a complete clean-room rewrite is happening in conjunction with this change.
hey cofounder here. since it takes my 16 year old neighbors son 15 mins and $100 claude code credits to hack your open source project
Are you at all worried that the message you are spreading here is "We are no longer confident in our own ability to secure your data?"
That's exactly the message I got from the video
Right, but those capabilities are available to you as well. Granted the remediation effort will take longer but...you're going to do that for any existing issues _anyway_ right?
I understand why this is a tempting thing to do in a "STOP THE PRESSES" manner where you take a breather and fix any existing issues that snuck through. I don't yet understand why when you reach steady-state, you wouldn't rely on the same tooling in a proactive manner to prevent issues from being shipped.
And if you say "yeah, that's obv the plan," well then I don't understand what going closed-source _now_ actually accomplishes with the horses already out of the barn.
> those capabilities are available to you as well
Give him $100 to obtain that capability.
Give each open source project maintainer $100.
Or internalize the cost if they all decide the hassle of maintaining an open source project is not worth it any more.
I'm not aiming this reply at you specific, but it's the general dynamic of this crisis. The real answer is for the foundational model providers to give this money. But instead, at least one seems to care more about acquiring critical open source companies.
We should openly talk about this - the existing open source model is being killed by LLMs, and there is no clear replacement.
I don't think this really helps that much. Your neighbor could ask an LLM to decompile your binaries, and then run security analysis on the results.
If the tool correctly says you've got security issues, trying to hide them won't work. You still have the security issues and someone is going to find them.
If I understand correctly, their primary product is SaaS, and their non-DIY self-host edition is an enterprise product. So your neighbor wouldn't have access to the binaries to begin with.
It only takes 20 minutes and $200 to hack a closed source one too though. LLMs are ludicrously good at using reverse engineering tools and having source available to inspect just makes it slightly more convenient.
Very true, but that is still a meaningfully higher cost at scale. If, as people are postulating post-Mythos, security comes down to which side spends more tokens, it is a valid strategy to impose asymmetric costs on the attacker.
Couldn't you just spend those $100 on claude code credits yourself and make sure you're not shipping insecure software? Security by obscurity is not the correct model (IMO)
Why not can’t you (as in Cal.com) spend that amount of money and find vulnerabilities yourself?
You can keep the untested branch closed if you want to go with “cathedral” model, even.
What makes you think it'll take him more than 16 mins and $110 claude code credits to hack your closed source project?
whooptie fuggin doo, then spend $200 on finding and fixing the issues before you push your commits to the cloud
> neighbors son 15 mins and $100 claude code credits
Is that true? Didn't the Mythos release say they spent $20k? I'm also skeptical of Anthropic here doing essentially what amounts to "vague posting" in an attempt scare everyone and drive up their value before IPO.
Please, go ahead!
> since it takes my 16 year old neighbors son 15 mins and $100 claude code credits to hack your open source project
To what end? You can just look at the code. It's right there. You don't need to "hack" anything.
If you want to "hack on it", you're welcome to do so.
Would you like to take a look at some of my open-source projects your neighbour's kid might like to hack on?
*This comment sponsored by Anthropic
It's funny that this news showed up just as we (Xata) have gone the other direction, citing also changes due to AI: https://xata.io/blog/open-source-postgres-branching-copy-on-...
We did consider arguments in both directions (e.g. easier to recreate the code, agents can understand better how it works), but I honestly think the security argument goes for open source: the OSS projects will get more scrutiny faster, which means bugs won't linger around.
Time will tell, I am in the open source camp, though.
This certainly makes me feel better about the project I started a few months ago to replace my Cal.com instance with a smaller, simpler self-hosted tool
https://git.sr.ht/~bsprague/schedyou
I am beyond convinced at this point that you either run an Open Source Project with a small revenue company (single digit millions) or run a software company that does more than 10M ARR at the least and be closed source. I know there are exceptions but most open source Software companies are providing code with heavy restrictions or teaser features and gate keep everything in their "ee/enterprise" version etc.
I know plenty of security researchers who exclusively use Claude Code and other tools for blackbox testing against sites they don’t have the source code for. It seems like shutting down the entire product is the only safe decision here!
The real threat is not security but bad actors copying your code and calling it theirs.
IMHO, open source will continue to exist and it will be successful but the existence of AI is deterrent for most. Lets be honest, in recent times the only reason startups went open source first was to build a community and build organic growth engine powered by early adaptors. Now this is no longer viable and in fact it is simply helping competitors. So why do it then?
The only open source that will remain will be the real open source projects that are true to the ethos.
I agree with you that AI's disruption of attribution is a much bigger problem, but it's also worth recognizing that not everyone has this same motivation. It mostly affects copyleft open source licenses.
Attribution isn't required for permissive many open source licenses. Dependencies with those licenses will oftentimes end up inside closed source software. Even if there isn't FOSS in the closed-source software, basically everyone's threat model includes (or should include) "OpenSSL CVE". On that basis, I doubt Cal is accomplishing as much as they hope to by going closed source.
> The real threat is not security but bad actors copying your code and calling it theirs.
How has this changed?
Bad actors can rewrite it with AI and claim ownership of the result.
In my advisory job founders always raise the question about open sourcing within the first hour of meeting me. They think that open sourcing product means transparency and developer trust which helps with early adoption. Every single founder I talked to brings up open source as a market penetration method to drive the initial adoption.
I always say to just stop with the virtue signaling led sales technique.
I despise the "we are like the market leader of our niche but open source" angle. Developer as a buyer and as a community these days in my opinion do not care about open source anymore. There is no long term value to that. The moment a product gets traction the open source elements is a constant mild headache as open source product means that they have no intellectual copyright on the core aspect of the product and it is hard to raise money or sell the company. And whenever a product gets traction they will take any excuse to make it close source again. With an open source product they are just coasting on brand. Regardless of what your personal opinion is, this has been largely true for most for-profit business.
Open source is largely is nothing more then a branding concept for a company who is backed by investors.
Sounds backwards to me.
> Today, we are making the very difficult decision to move to closed source, and there’s one simple reason: security.
It seems like an easy decision, not a difficult one.
Today, it's easy to (publicly) evaluate the ability of LLMs to find bugs in open source codebases, because you don't need to ask permission. But this doesn't actually tell us the negative statement, which is that an LLM won't just as effectively find bugs in closed codebases, including through black-box testing, reverse engineering, etc.
If the null hypothesis is that LLMs are good at finding bugs, full stop, then it's unclear to me that going closed actually does much to stop your adversary (particularly as a service operator).
Think this is a bad, bad move...
https://news.ycombinator.com/item?id=47780712
Juxtapose this with the fact that many HNers will decry strong copyleft FOSS licenses as not being truly "open source" - the reality is that closed source software is still full of open-source non-copyleft dependencies. Unless you're rolling your own encryption and TCP stack, being closed source will not be the easy solution that many imagine it to be.
- You know, Lindsay, as a software engineering consultant, I have advised a number of companies to explore closing their source, where the codebase remains largely unchanged but secure through obscurity.
- Well, did it work for those companies?
- No, it never does. I mean, these companies somehow delude themselves into thinking it might, but... but it might work for us.
Monumentally dumb given their codebase is already public and the type of security issues that exist in software are usually found in the oldest code. But also, and more importantly, cal.com launched coss.com last year, open source is (ostensibly) their DNA. How could they do a complete 180 on something so fundamental and think that wouldn’t worry customers, much more so than their codebase being public? I cannot even begin to understand this. Surely there must be more to the story?
Coss.com reads like a half assed pivot if you look at it with today's news. It's clear cal.com isn't making enough money and going closed source is yet another attempt to fix that.
Oh wow the coss.com thing makes this so much worse. Making such an aggressive and public commitment to open source to then turn around and do something like this is a pretty rough look.
TIL I learned about yet another calendar application I don't need. Someone should setup their openclaw to just write a new todo/calendar app each week; they'll be billionaires by the end of the year.
Could you not simply point AI at your open source codebase and use it to red-team your own codebase?
This post's argument seems circular to me.
Who even uses their open source product?
AI sure is useful as a scapegoat for any negative PR inducing moves.
I guess why fix vulnerabilities when you can just obscure them?
Saaspocalypse is coming for cal.com
Good for them. I’m sure they saw the writing on the wall when Monday.com was cloned. This is the right move.
I hate how this sounds...but this reads to me "we lack the confidence in our code security so we're closing the source code to conceal vulnerabilities which may exist."
This is some truly exceptionally clownish attention seeking nonsense. The rationale here is complete nonsense, they just wanted to put "because AI" after announcing their completely self-serving decision. If AI cyber offense is such a concern, recognize your role as a company handling truckloads of highly sensitive information and actually fix your security culture instead of just obscuring it.
I mean it's not complete nonsense, but yeah, doing it for security reasons sounds like BS. I actually thought this was going to be about how AI makes it super easy for someone to steal all their code and fold it into their own competing project. I've seen a few open source projects get sideswiped by this, AI is pretty good at copying code (and obfuscating the fact that it was copied). I suspect that's the real reason but it doesn't sound as good. So they went with this half-truth.
Risk tolerance and emotional capacity differs from one individual to another, while I may disagree with the decision I am able to respect the decision.
That said, I think it’s important to try and recognize where things are from multiple angles rather than bucket things from your filter bubble alone, fear sells and we need to stop buying into it.
This seems dishonest, like someone is forcing the decision for other reasons, and they're using security and AI as a distraction.
This is the future now that AI is here. Publishing is going to be dead, look at the tea leaves, how many engineers are claiming they don’t use package managers anymore and just generate dependencies? 5 years and no one will be making an argument for open source or blogging.
Security through obscurity has been known to be a faulty approach for nearly 200 years. Yet here we are.
Seems like it's just being used as a convenient pretense to back out of open-source.
I mean, they were a COSS startup using the AGPLv3, so checks out. :)
Changed the license of the foss version cal.diy to MIT . Grace in disguise , now enterprise user can host cal.diy without worries of viral licensing .
This has to be the most bullshit reason I've seen.. if AI can be pointed and find vulnerabilities then do it yourself before publishing the code.
> if AI can be pointed and find vulnerabilities then do it yourself before publishing the code
At your cost.
Every time you push. (or if not that, at least every time there is a new version that you call a release)
Including every time a dependency updates, unless you pin specific versions.
I assume (caveat: I've not looked into the costs) many projects can't justify that.
Though I don't disagree with you that this looks like a commercial decision with “LLM based bug finders could find all our bad code” as an excuse. The lack of confidence in their own code while open does not instil confidence that it'll be secure enough to trust now closed.
For-profit companies using open-source software should bear that cost - that's my position.
I believe than N companies using an open source project and contributing back would make this burden smaller than one company using the same closed-source project.
You know what?
Great move.
Open-source supporters don't have a sustainable answer to the fact that AI models can easily find N-day vulnerabilities extremely quickly and swamp maintainers with issues and bug-reports left hanging for days.
Unfortunately, this is where it is going and the open-source software supporters did not for-see the downsides of open source maintenance in the age of AI especially for businesses with "open-core" products.
Might as well close-source them to slow the attackers (with LLMs) down. Even SQLite has closed-sourced their tests which is another good idea.
The tools are available to everyone. It's becoming easier for hackers to attack you at the same speed that it's becoming easier for you to harden your systems. When everyone gains the same advantage at the same time, nothing has really changed.
It makes me think of how great chess engines have affected competitive chess over the last few years. Sure, the ceiling for Elo ratings at the top levels has gone up, but it's still a fair game because everyone has access to the new tools. High-level players aren't necessarily spending more time on prep than they were before; they're just getting more value out of the hours they do spend.
I agree it's a shit tactic, but one thing I can say for those running software businesses is that it's not an equivalent linear increase on both sides. It's asymmetric, because # of both attackers and the amount of attack surface (exposed 3rd party dependencies, for example) is near infinite, with no opportunity cost for failure by the bad actors (hackers). However a single failure can bring down a company, particularly when they may be hosting sensitive user data that could ruin their customers' businesses or lives.
I think Cal are making the wrong call, and abandoning their principles. But it isn't fair to say the game is accelerating in a proportionate way.
See: https://www.youtube.com/watch?v=2CieKDg-JrA
Ultimately, he concludes that while in the short run the game defines the players' actions, an environment that makes cooperation too risky naturally forces participants to stop cooperating to protect themselves from being "exploited" (this bit is around 34:39 - 34:46)
Sure, I can see that to a degree. And there definitely is a bit of chaos during the transition period as everyone scrambles to figure out what the landscape looks like now. I could understand if they decided to temporarily do less-frequent code releases, or maybe release their code on a delay or something, while they wait for the dust to settle. But I don't think permanently ending open source development is the right move.
Agreed! There must be a way to maintain the principles and benefits of open-source; the alternative, which is that all software becomes a black box, is antithetical to the same security that that choice supposedly aims to achieve.
I think companies make decisions like this from a tactics level, not realizing that by doing so they are not only alienating their customers but misunderstanding the basic (often unconscious or unspoken) social contract upon which their very existence is predicated.
Calendly already existed. Cal came along and said, ok, but what if the code were out in the open -- auditable, self-hostable. Then you wouldn't have to worry about lock-in, security, privacy, etc, in the same way. Now they are removing that entire aspect of their value prop. It may be the only thing that caused a good portion of their customers to adopt in the first place.
Haven't the SQLite tests always been closed? Getting access to them is a major reason for financially supporting them
> especially for businesses with "open-core" products.
Then good, that overengineered, intentionally-crippled crap should go away.