If they can't, why not?
If they can, why haven't they already?
If you only tell them to find issues in PHP - the strongest models probably still can, although they might find different issues ;)
The original exploit, and then when the rumors of a big critical patch got out, the people who are leaking the details online probably used an LLM to find the exploit again.
Just revealing that an unpatched exploit exists in $XYZ these days basically guarantees that a bunch of people are going to target $XYZ with LLMs looking for that exploit.
Well, that would be super nice of them.
From a Machiavellian standpoint it may benefit the people with the most powerful models to let some serious RCEs like this PHP one get widely exploited in damaging ways to further their regulatory capture argument that open weight models have to be legally banned and only locked down models with enforced guardrails around usage can be allowed.
From a marketing standpoint, having the first model to find a bug of this magnitude and severity would be a pretty damn impressive proof of capability. Finding previously unknown, critical vulnerabilities in widely used open-source software could become a gold-standard test of frontier AI competence.
Either Mythos is useless and didn't find this (hint: Opus 5.5 will find this once it knows where to look)... or, they did find it, and this is one of many vulnerabilities they're covering up via "guardrails".
I'll be a lot happier if I wake up tomorrow and find this was found with help from Anthropic (or even OpenAI) but I won't hold my breath.
The bad guys have invested the resources of the criminal enterprise into hardware running unrestricted models.