Anthropic's Mythos finds decade-old bugs in Firefox
What's the story
Anthropic's latest AI model, Mythos, has revolutionized the way Mozilla approaches cybersecurity for its Firefox browser. The advanced system has detected a large number of high-severity bugs in the software, some of which had been hidden in the code for over a decade. This marks a major leap from what AI security tools could do just six months ago.
Enhanced capability
AI's bug-finding capabilities have drastically improved
The latest generation of AI bug-finding tools, like Mythos, has improved significantly. They can now evaluate their own work and eliminate bad results, reducing the number of low-quality reports and false positives. Mozilla's researchers noted this dramatic shift in just a few months. In April 2026 alone, Firefox released 423 bug fixes compared to only 31 in the same month last year.
Advanced detection
Mythos even uncovered vulnerabilities in Firefox's 'sandbox' system
Mythos has even uncovered vulnerabilities in Firefox's "sandbox" system, a feat that requires a highly sophisticated attack. The model must create a malicious patch for the browser and then exploit the most secure part of the software with this new code. This multi-step process is both creative and meticulous, highlighting Mythos's advanced capabilities.
Human intervention
Firefox team not using AI to fix bugs yet
Despite the progress in AI coding tools, the Firefox team isn't using AI to fix bugs. They do ask AI to code patches for each bug, but the resulting code usually can't be deployed directly. Instead, it serves as a model for a human engineer. "For the bugs we're talking about in this post, every single one is one engineer writing a patch and one engineer reviewing it," Brian Grinstead, an engineer at Mozilla, told TechCrunch.
Future implications
Long-term effects on cybersecurity still unknown
The long-term effects of AI's capabilities on cybersecurity remain uncertain. A month after Mythos was previewed, many of the bugs it found may not have been patched yet. This makes it difficult to assess their full impact. Anthropic CEO Dario Amodei expressed optimism that these new tools would ultimately benefit defenders, saying, "If we handle this right, we could be in a better position than we started."