Claude Mythos fixes 271 Firefox bugs, including one from 20 years ago

Mozilla said it used Anthropic’s Claude Mythos Preview and other AI tools to help find and fix 271 Firefox bugs.

The fixes landed in Firefox 150 and patch releases 149.0.2, 150.0.1, and 150.0.2, including long-standing security issues.

Some vulnerabilities dated back 15 to 20 years, showing how AI-assisted analysis can uncover flaws traditional fuzzing may miss.

Mozilla also built an agentic fuzzing pipeline to generate reproducible test cases and speed up triage and patching.