Mozilla says Anthropic’s Mythos is ‘every bit as capable’ as ‘the world’s best security researchers’ after Firefox experiment — and says the ‘zero-days are numbered’

A graphical rendering of the Mozilla Firefox icon.

• Mozilla used Anthropic’s Mythos AI to find hundreds of Firefox vulnerabilities, matching top human researchers in capability
• The experiment suggests AI can now reason through code to uncover complex bugs at scale
• This shift could reduce the advantage attackers have traditionally had in discovering valuable zero-day vulnerabilities

Mozilla thinks AI could change how bugs are found for good — so it turned a version of the Claude model loose on its own browser code. The company's security team has spent the past few months collaborating with Anthropic and testing an early version of the Claude Mythos Preview model against its browser code.