Mozilla says 271 vulnerabilities found by Mythos have 'almost no false positives'

Mozilla ran an agentic harness powered by Claude Mythos Preview across Firefox's source code, identifying 271 security bugs fixed in Firefox 150 . The breakthrough was achieved through improvements in the models themselves and Mozilla's development of a custom "harness" that supported Mythos as it analyzed Firefox source code . Mozilla reported fewer than 15 false positives total, which were primarily caused by changing preconditions needed to trigger issues .

Source: Ars Technica | 2026-05-07