Firefox finds 20 year old bug and patches 14 months of fixes in 30 days using Anthropic’s Mythos AI

Mozilla’s latest Firefox security update provides a rare glimpse into what happens when frontier AI capabilities reach defenders before attackers. The company said it fixed 423 Firefox security bugs in April after gaining access to Claude Mythos Preview, compared with roughly 420 fixes over the previous 14 months. That compression is the signal. The defensive side did in one month what had previously taken more than …