I am sceptical because AI companies, and anthropic in particular, like to overplay their achievements and build undeserved hype. I also don't understand all the caveats (maybe official announcement is more clear what this really means).

But yeah, if their model can reliably write an exploit for novel bugs (starting from a crash, not a vulnerable line of code) then it's very significant. I guess we'll see, right?

edit: Actually the original post IS dramatic: "Has Mythos just broken the deal that kept the internet safe? For nearly 20 years the deal has been simple: you click a link, arbitrary code runs on your device, and a stack of sandboxes keeps that code from doing anything nasty". Browser exploits have existed before, and this capability helps defenders as much as it helps attackers, it's not like JS is going anywhere.