Mandiant Says Hijacked AI Coding Assistant Session Spread Shai-Hulud Across About 100 Repositories

Mandiant has disclosed a software-supply-chain intrusion in which an attacker hijacked an active AI coding-assistant session at an unnamed SaaS provider and used the trusted developer workflow to spread the Shai-Hulud worm across approximately 100 internal repositories. The case, published in the September 2026 AI Risk and Resilience report, is one of the clearest public examples yet of an AI-assisted development environment becoming part of an attack path rather than merely a target.