Firefox 150 Fixes 271 Vulnerabilities Identified Through Anthropic's Claude Mythos Preview Collaboration
An early version of Claude Mythos Preview was applied to Firefox as part of a continued collaboration with Anthropic. This initial evaluation identified 271 vulnerabilities, which were addressed in the release of Firefox 150 this week. The experience demonstrates that teams can overcome challenges through focused effort and reprioritization. While the work remains ongoing, significant progress has been made, offering defenders a decisive advantage. Simon Willison collected this quotation from Bobby Holley and posted it on April 22, 2026.
Key facts
- Firefox 150 was released this week
- The release fixes 271 vulnerabilities
- Vulnerabilities were identified through initial evaluation of Claude Mythos Preview
- Claude Mythos Preview is an early version from Anthropic
- The work involved collaboration between Firefox and Anthropic
- Simon Willison collected the quotation from Bobby Holley
- The quotation was posted on April 22, 2026
- The work demonstrates that focused effort can help defenders win decisively
Entities
Artists
- Bobby Holley
- Simon Willison
Institutions
- Anthropic
- Firefox