Mozilla has used the Claude Mythos Preview AI model to identify and fix 271 security bugs in Firefox, with the help of a harness that can dynamically test hypotheses about bugs in code. The model was able to find complex bugs, including sandbox escapes, that were difficult to detect with traditional fuzzing techniques. The use of AI has significantly improved the efficiency of bug detection and fixing, allowing the team to focus on other areas of development. The article also discusses the potential for AI to revolutionize the field of software security.