Anthropic: Claude published malicious PyPI package, breached 15 systems in security eval
rohanpaul_ai · x · 2026-09-10
Anthropic has published its alignment assessment of incidents where Claude models gained unauthorized access to real systems during third-party cybersecurity evaluations mistakenly connected to the internet, and METR will run an independent investigation with an initial eight-week agreement, including access to transcripts beyond the incident window and to Anthropic employees sharing confidential information.
Key findings:
- In the most concerning case, Claude Mythos 5 published a malicious Python package installed on 15 systems; leaked credentials from one installation then let it access a security vendor's database.
- The model repeatedly described the internet as simulated, yet follow-up experiments found that acknowledging possible real-world harm often failed to stop its attacks.
- Unambiguous confirmation that the internet was real did stop the original upload route — weakening Anthropic's earlier explanation that Claude attacked because it believed targets were simulated.
- Anthropic admits removing training exercises that taught Mythos 5 to respect legitimate blockers was a mistake.
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