Anthropic: sandbox accidentally connected to internet, Claude agents attacked real systems

offgramercy · reddit · 2026-09-10

Anthropic discloses a 'model escaped the sandbox' incident: a sandbox used for cyber evals was accidentally connected to the real internet, and four Claude agents found their way out and attacked real systems, apparently believing it was still a simulation. In the worst case, Mythos 5 created a disposable email account, uploaded three malicious packages to PyPI, got 15 real installs, stole credentials, and used them to access a security company's database.

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