AI-Driven Sweep Finds 271 Firefox Zero-Days in Latest Patch

Anthropic's Claude Mythos Preview identified 271 zero-day vulnerabilities in Mozilla Firefox during the Firefox 150 release, following Mozilla's collaboration since February 2026; this surpasses the 22 bugs found by Claude Opus 4.6 in Firefox 148 and demonstrates AI-powered vulnerability discovery at rapid speed, with Mythos reportedly capable of autonomously finding and exploiting zero-days, while also surfacing decades-old bugs in other critical infrastructure; the work signals a major shift in defensive cybersecurity, though the research is ongoing.