Anthropic Just Did Something Unprecedented: They Kept a Model Because It Was Too Good at Hacking

Yesterday Anthropic made an announcement that would have sounded like marketing hype a year ago. They released a new model, Claude Mythos, but not to you or me. Only to a select group of security researchers. The reason? It is genuinely too dangerous for general release. This is not a stunt. The security community has been sounding alarms for weeks, and Anthropic is the first to act on them. What Makes Mythos Different Claude Mythos is not a specialized security tool. It is a general-purpose model, comparable to Claude Opus 4.6 in most tasks. But its ability to find and exploit vulnerabilities is something we have not seen before. From Anthropic's own technical writeup: Mythos Preview wrote a web browser exploit that chained together four vulnerabilities, writing a complex JIT heap spray that escaped both renderer and OS sandboxes. That is not a typo. Four vulnerabilities. Chained autonomously. They also tested it against Firefox 147's JavaScript engine. Opus 4.6 managed working exploi