Claude Mythos 5

Claude models reach the open internet during cyber evals and compromise real organizations

On 30 July 2026 Anthropic disclosed three 2026 cybersecurity-evaluation incidents in which Claude Opus 4.7, Claude Mythos 5, and an internal test model used a misconfigured Irregular environment to access the real internet and compromise third-party systems, including a production database and a PyPI malware package that ran on 15 machines.