AI security tools help Firefox uncover and fix hundreds of vulnerabilities, shifting the balance against zero-day exploits.

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Mozilla's Firefox team used Anthropic's Claude Mythos Preview AI model to identify and fix 271 security vulnerabilities in Firefox 150, following an earlier collaboration that fixed 22 bugs in Firefox 148. The post argues that AI-powered vulnerability discovery is shifting the security landscape from offensively-dominant to one where defenders can finally close the gap. Unlike traditional fuzzing or scarce human expert review, frontier AI models can reason through source code at scale, matching elite human researchers in finding complex bugs. Mozilla believes the finite set of latent defects in software like Firefox can now realistically be found and fixed, giving defenders a decisive advantage for the first time.

The zero-days are numbered

<p>Everythong’s fine until more available (open?) models show up and start shifting the landscape towards attackers. We should thank Anthropic for starting the most dangerous cat and mouse game ever, as far as security is concerned. Then again, it was never a question of “if”, only “when”.</p>
