Claude Uncovers 22 Firefox Vulnerabilities

🔑 Enhanced Key Takeaways

• •Mozilla fixed the 22 security vulnerabilities plus 90 non-security bugs in Firefox version 148.0 released on February 24, 2026[2][3][7].
• •Claude Opus 4.6 discovered a Use After Free vulnerability in Firefox's JavaScript engine within 20 minutes, leading to 50 more crashing inputs by submission time[3][5].
• •Claude successfully generated crude exploits for 2 vulnerabilities in test environments without sandbox protections, costing $4,000 in API credits[3][4][5].

🛠️ Technical Deep Dive

• •Claude exploited CVE-2026-2796 via Use After Free (UAF) causing type confusion, enabling info leak through wrong field reads, arbitrary read/write primitives (read64/write64 using JavaScript and WebAssembly), and function pointer overwrite for code execution[4].
• •Exploitation chain: UAF → type confusion (stale pointer to different object) → addrof (leak object address) and fakeobj (forge JS object) → fake ArrayBuffer with controlled backing store pointer → arbitrary R/W over process address space[4].
• •Exploits demonstrated file read/write on unsandboxed js shell mimicking browser content process, but failed against full Firefox defenses like sandbox[4][5].

🔮 Future ImplicationsAI analysis grounded in cited sources

⏳ Timeline