Claude Mythos Found 271 Zero-Days in Firefox 150. This Is What the New World Looks Like.
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Discussion of the blog article Claude Mythos Found 271 Zero-Days in Firefox 150. This Is What the New World Looks Like..
In February, Anthropic's Frontier Red Team used Claude Opus 4.6 to find 22 vulnerabilities in Firefox in two weeks — more than were reported in any single month in all of 2025. Then Mythos arrived. Firefox 150, released today, patches 271 vulnerabilities found by Claude.
Discussion thread — share findings, corrections and follow-ups below.