tech

May 9, 2026

A company tested Claude Mythos Preview. It says the AI found a bug that existed for 20 years

Mozilla says Anthropic's unreleased Claude Mythos AI found security flaws that automated testing systems missed for years.

A company tested Claude Mythos Preview. It says the AI found a bug that existed for 20 years

TL;DR

  • Mozilla used Anthropic's unreleased Claude Mythos Preview AI to find security flaws.
  • The AI model discovered hundreds of issues, including one that had existed for 20 years.
  • This AI-assisted effort contributed to fixes for 423 security bugs in Firefox's April releases.
  • Previous AI models generated incorrect solutions, but newer models can navigate complex codebases.
  • Claude Mythos is not publicly released due to potential national security and online crime risks.
  • Mozilla plans to integrate AI analysis further into Firefox's development pipeline.