# Mozilla released Firefox 150 with fixes for 271 security vulnerabilities identified by Anthropic’s Claude Mythos Preview.

*genai · news · 2026-04-22 · TNW*

## Key points

- Anthropic's unreleased Claude Mythos Preview AI found 271 security vulnerabilities in Firefox 150 alone.
- Claude Mythos can autonomously execute multi-stage network attacks, as confirmed by the UK AI Security Institute.
- Project Glasswing restricts Mythos access to 12 core partners and around 40 approved defensive organisations.
- An unauthorized group accessed Mythos Preview on launch day by guessing the model’s vendor URL.
- Anthropic has used Mythos to identify thousands of zero-days in all major operating systems and browsers.

**Companies:** Amazon Web Services, Apple, Google, Microsoft, Nvidia, Broadcom, Cisco, CrowdStrike, JPMorganChase, Palo Alto Networks
**Countries:** UK, USA

[Read the full story on TNW](https://thenextweb.com/news/mozilla-firefox-claude-mythos-271-vulnerabilities)

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