Firefox has begun using an advanced AI model, Claude Mythos, to identify and fix security vulnerabilities in its browser, successfully resolving as many as 271 flaws and marking a significant shift in how software security is managed.

Mozilla uses Anthropic’s Mythos to match human expertise in finding bugs

The FOSS outfit on Tuesday reminded readers that it used Anthropic’s Opus 4.6 model to look for bugs in Firefox 148 and found 22 bugs. Mythos found 271 vulnerabilities in Firefox 150. Mozilla CTO Bobby Holley expressed mixed feelings about that result,

Apple has released iOS 26.4.2 with unspecified bug fixes and a single security patch, while Mozilla’s Firefox 150 adds PDF editing tools, improved split view, and addresses 41 security vulnerabilities. Both updates underscore a broader push for timely ...

The vulnerability allowed tracking across sites, even in Private Mode.

Mozilla’s partnership with Anthropic is really paying off. In March, it announced that Anthropic’s Frontier Red Team had helped it find and fix 22 security-sensitive bugs and 90 other bugs in Firefox. But this month’s bounty is even bigger: Firefox 150 is out today with fixes for 271 vulnerabilities.

Firefox 150 is now available with Split View upgrades, improved PDF editing, and stronger security protections across all platforms.