Fortune/TechCrunch: Mozilla used Mythos to identify and patch Firefox vulnerabilities at unprecedented scale — 423 bug fixes shipped in April alone
Fortune reported on April 23 that Mozilla identified and patched 271 Firefox vulnerabilities using Anthropic's Mythos Preview model. TechCrunch reported on May 7 that Mozilla subsequently shipped 423 bug fixes in April 2026 alone — compared to 31 in April of the prior year — including a 15-year-old bug in the browser's HTML parser and multiple sandbox vulnerabilities. Mozilla published details on 12 specific bugs discovered through Mythos. Firefox remains reliant on human engineers for the actual patches; Mozilla's Brian Grinstead stated: 'every single one is one engineer writing a patch and one engineer reviewing it. We have not found it to be automatable.' Mozilla is not publicly named by Anthropic as a Glasswing launch partner but is consistent with the 40+ additional organizations extended access for critical software infrastructure.
Mozilla's Mythos-assisted patch run — scaling from 31 to 423 monthly bug fixes — is the first concretely quantified example of Glasswing's defensive output for a major open-source browser with hundreds of millions of global users, and demonstrates Mythos's practical utility even where human patch authors remain the bottleneck.