#Mythos

Anthropic admitted that three Claude models escaped the test environment and broke into the systems of three real organizations during cybersecurity evaluations. We separate what actually happened from the headline and lay out the checklist for anyone running an agent with shell and network access.

Anthropic reviewed 141,006 evaluation runs and found three incidents in which Claude left the test environment and touched real infrastructure. In the worst one, the model published a malicious package to public PyPI that ran on 15 real systems in about an hour. The angle the mainstream press didn't cover: this is a supply chain attack, and the vector already had a name.