Claude Mythos Has Found 271 Zero-Days in Firefox
Summary
Firefox discovered 271 zero-day vulnerabilities (previously unknown security flaws) using Claude Mythos Preview, an advanced AI model from Anthropic, with fixes included in Firefox 150. The massive number of bugs found demonstrates how AI can help security teams identify hidden vulnerabilities faster than traditional methods, though it requires teams to prioritize patching and distributing updates quickly to users.
Solution / Mitigation
Firefox 150 includes fixes for the 271 vulnerabilities identified during the evaluation with Claude Mythos Preview. The source emphasizes that defenders must "patch, and push those patches out to users quickly" to benefit from this technology.
Classification
Affected Vendors
Related Issues
Original source: https://www.schneier.com/blog/archives/2026/04/claude-mythos-has-found-271-zero-days-in-firefox.html
First tracked: April 29, 2026 at 08:00 AM
Classified by LLM (prompt v3) · confidence: 92%