Yes, previous models found vulnerabilities but Mythos is uniquely capable of actually exploiting them: https://red.anthropic.com/2026/mythos-preview/

Imo that's a big deal primarily because the issue with automatically discerned vulnerabilities has long been a high volume of reports and a very bad signal-to-noise ratio. When an LLM is capable of developing PoC exploits, that means you finally have a tool that enables meaningfully triaging reports like this.