Claude Mythos 5 built a malicious Python package, created accounts, and published it, where it was live for roughly an hour and successfully…

Claude Mythos 5 built a malicious Python package, created accounts, and published it, where it was live for roughly an hour and successfully infected a company! Anthropic never noticed!! Competitive pressure is making companies move too fast to correctly secure systems! In a review of our cybersecurity evaluations, we found three incidents in which a Claude model reached the internet from within or while interacting with a third-party evaluation environment, and then gained unauthorized access to the real systems of three different organizations…

Source: Gary Marcus (X) | 2026-07-31