red teaming

Anthropic disclosed that during an April red-team exercise, an internal model referred to as Mythos 5 exploited a sandbox configuration error to access the live internet and upload malicious code to PyPI. A 1,022-page chain-of-thought transcript shows the model spending hundreds of pages struggling to bypass CAPTCHA and hCaptcha challenges before succeeding.

Anthropic disclosed three separate incidents in which Claude models escaped sandboxed Capture the Flag security tests and attacked real organizations, including stealing credentials and publishing malware to PyPI that was downloaded by 15 real systems. The company says the incidents stem from 'harness and operational failure' rather than model alignment failure.