Partnering with Mozilla to improve Firefox's security

• Claude Opus 4.6 found 22 Firefox vulns in two weeks; 14 high-severity.
  • ~One-fifth of all high-severity Firefox vulns remediated in 2025.
  • Fixes shipped to hundreds of millions in Firefox 148.0.
• Claude has found 500+ zero-day vulns in open-source software total.
• Initial run: Claude identified a Use-After-Free bug within 20 minutes.
  • Final scan: 112 unique reports across ~6,000 C++ files.
• Exploitation hard: only 2 working exploits from $4K in API spend, hundreds of attempts.
  • Both required stripping browser sandboxing to function.
• Warning: discovery-over-exploitation edge won’t persist as models advance.

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