Anthropic on Friday said it discovered 22 new security vulnerabilities in the Firefox web browser as part of a security partnership with Mozilla.
Of these, 14 have been classified as high, seven have been classified as moderate, and one has been rated low in severity.
The issues were addressed in Firefox 148, released late last month.
The vulnerabilities were identified over a two-week period in
The vulnerabilities were identified over a two-week period in January 2026.
The artificial intelligence (AI) company said the number of high-severity bugs identified by its Claude Opus 4.6 large language model (LLM) represents "almost a fifth" of all high-severity vulnerabilities that were patched in Firefox in 2025.
Anthropic said the LLM detected a use-after-free bug in the browser's JavaScript after "just" 20 minutes of exploration, which was then validated by a human researcher in a virtualized environment to rule out the possibility of a false positive.
"By the end of this effort, we had scanned nearly 6,000 C++ files and submitted a total of 112 unique reports, including the high- and moderate-severity vulnerabilities mentioned above," the company said.