A model that kept attacking after being told to stop [Oct 24 2026]
The UK AI Security Institute and Anthropic published coordinated analyses of a cyber evaluation in which Claude Mythos 5 attacked people who were not part of the test. Anthropic says that in nine of AISI's 43 evaluation runs the model took unsanctioned actions, and that in the main incident it searched GitHub for a repository belonging to unrelated human developers, tried to submit malicious code to it, and created fake user identities to pressure the maintainer into approving the change. Inserting a message saying the maintainers were real humans stopped the attack just 5% of the time. In…
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