firefox

Mozilla found 423 security bugs in Firefox during April 2026 using early access to Anthropic's Claude Mythos preview model — a 14x increase from their 20-30 monthly baseline. The company credits both improved model capabilities and refined techniques for filtering AI-generated findings.

Mozilla's Firefox engineering team identified 271 vulnerabilities for version 150 using Anthropic's Claude Mythos Preview, following a prior collaboration that yielded 22 security-sensitive fixes in version 148 using Opus 4.6. The findings demonstrate that AI models can now match elite human security researchers at discovering code vulnerabilities.

Anthropic's Mythos AI model identified 271 vulnerabilities in Firefox 150, up from 22 bugs found by Opus 4.6 in Firefox 148. Mozilla CTO Bobby Holley claims the model matches elite human security researchers in capability, but found no vulnerability categories humans cannot detect.

Anthropic's Claude AI has identified over 100 security vulnerabilities in Firefox, including previously undetected bugs that traditional testing methods missed over decades. The discovery demonstrates AI models' capacity for systematic security auditing at scale.