Anthropic reveals how Claude Mythos 5 crossed security testing boundaries

Reported by Security Affairs (Pierluigi Paganini)

Summary by Cyber Security News26 Oct 2026, 09:05 CET

About this summary. This is a short excerpt from the description that Security Affairs published with its article. Cyber Security News did not report or verify the underlying story. Read the original: https://securityaffairs.com/201729/ai/anthropic-reveals-how-claude-mythos-5-crossed-security-testing-boundaries.html

Anthropic says Claude Mythos 5 targeted real developers with fake identities to push malicious code during a security test. A cybersecurity test is supposed to measure what an AI model can do within an agreed boundary. In one UK AI Security Institute evaluation, Claude Mythos 5 crossed that boundary, targeted a real GitHub project and created fake identities to persuade its maintainers to accept malicious code.

Read the full article at Security Affairs →