Is Mythos dangerous? Mozilla says it discovered 271 critical bugs in Firefox that humans missed

Mozilla revealed that Anthropic’s Mythos AI helped identify 271 critical bugs in Firefox, including 12 severe vulnerabilities that had evaded detection for years. The flaws involved memory corruption, sandbox escape risks, and a 15-year-old HTML parsing issue, all of which could enable malicious code execution or privilege escalation. Mozilla’s findings validate Mythos’ ability to automate vulnerability discovery, a process traditionally reliant on manual, time-consuming testing. Anthropic has warned that Mythos’ capabilities could be exploited by attackers to accelerate zero-day vulnerability searches. While the AI model itself does not exploit systems, its ability to analyze vast codebases and generate proof-of-concept exploits shortens the time between discovery and potential misuse. Governments and organizations are closely monitoring its dual potential: strengthening cybersecurity defenses or increasing risks if misused. Mozilla’s report highlights a shift in AI-assisted bug detection, where earlier models produced low-quality reports but newer systems like Mythos deliver actionable insights. By integrating Mythos with internal fuzzing tools, the company uncovered flaws—such as a WebAssembly initialization bypass and a 16-bit layout overflow—that traditional methods missed. These bugs could allow arbitrary memory access or sandbox escapes, posing significant security threats. Among the disclosed vulnerabilities was a race condition in inter-process communication (IPC) that could manipulate IndexedDB reference counts, leading to use-after-free exploits. Another flaw involved misinterpreting raw NaN values as JavaScript object pointers, creating pathways for sandbox breaches. Mozilla also fixed a long-standing issue tied to HTML table behavior, where excessive rows triggered an overflow in a 16-bit field. Mozilla attributed 271 of the 423 security fixes shipped in Firefox 150’s April 2026 release cycle to Mythos Preview. The findings underscore the AI’s role in modern cybersecurity, where automated tools are increasingly relied upon to preemptively identify and patch vulnerabilities. While the technology offers defensive advantages, its accessibility raises ethical and security concerns about unintended consequences.