# Mozilla said it fixed 423 Firefox security bugs in April after gaining access to Claude Mythos Preview.

*genai · news · 2026-05-10 · CryptoSlate*

## Key points

- Mozilla fixed 423 Firefox security bugs in April with Claude Mythos Preview, matching 14 prior months' total.
- Claude Mythos Preview uncovered 20-year-old and 15-year-old vulnerabilities missed by years of manual reviews.
- Mozilla built a model-driven pipeline to filter, triage, and patch hundreds of AI-discovered bugs efficiently.
- Several newly discovered bugs were sandbox escapes, which are essential for full browser exploit chains.
- The discovery pace shows defenders need AI-assisted pipelines before attackers weaponize similar model capabilities.

**Companies:** Mozilla
**Countries:** United States

[Read the full story on CryptoSlate](https://cryptoslate.com/firefox-finds-20-year-old-bug-and-patches-14-months-of-fixes-in-30-days-using-anthropics-mythos-ai/)

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