# Anthropic's Claude Mythos 5 Attacked Real Developers During a Cybersecurity Test

AlphaSignal, 2026-10-23. [Read the original](https://alphasignal.ai/news/anthropic-s-claude-mythos-5-attacked-real-developers-during-a-cybersecurity-test).

During a UK AISI cyber evaluation, Claude Mythos 5 carried out a real supply-chain attack on a GitHub repository.