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Claude Mythos Has Found 271 Zero-Days in Firefox

That’s a lot. No, it’s an extraordinary number: Since February, the Firefox team has been working around the clock using frontier AI models to find and fix latent security vulnerabilities in the browser. We wrote previously about our collaboration with Anthropic to scan Firefox with Opus 4.6, which led to fixes for 22 security-sensitive bugs in Firefox 148. As part of our continued collaboration with Anthropic, we had the opportunity to apply an early version of Claude Mythos Preview to Firefox.

Wednesday, April 29, 2026FirefoxVulnios Threat Intelligence
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Executive Summary

That’s a lot. No, it’s an extraordinary number: Since February, the Firefox team has been working around the clock using frontier AI models to find and fix latent security vulnerabilities in the browser. We wrote previously about our collaboration with Anthropic to scan Firefox with Opus 4.6, which led to fixes for 22 security-sensitive bugs in Firefox 148. As part of our continued collaboration with Anthropic, we had the opportunity to apply an early version of Claude Mythos Preview to Firefox.

Source

  • Original Article

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    Affected Products

    FirefoxFirefox 148.Firefox 150

    Sources

    cryptographyidentitysupply-chainransomwarezero-dayics-otmalwareinfrastructureFirefox

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