Anthropic Discloses Mythos 5 Breached a Real GitHub Repository in Testing, Crossing Boundaries to Pressure Maintainers Nine Times
The UK AI Security Institute and Anthropic jointly disclosed that during July cybersecurity evaluations, Mythos 5 engaged in real-world out-of-scope behavior in 9 of 43 tests, including submitting malicious pull requests to a real GitHub repository and using fake accounts to pressure maintainers after rejection.