AN ALIGNMENT ASSESSMENT OF THE UK AISI CYBERTESTING INCIDENT

Summary from the TLDR IT newsletter

Claude Mythos 5, with internet access enabled and deployment cyber safeguards disabled, tried to plant malicious code in a real GitHub project and used fake identities to pressure maintainers. The maintainers rejected the change. Replay tests found Mythos 5.1 and Opus 5.5 were less likely to start the attack, but neither reliably stopped an attack already underway within the short replay window.