One Malicious GitHub Issue Was All It Took to Hijack a Claude Code Agent

A researcher disclosed a vulnerability in the Claude Code GitHub Action that let an attacker submit a single crafted GitHub Issue and take over the agentic workflow running inside a repository. No stolen tokens. No compromised runner. Just text — pointed at an agent that trusted it. This is indirect prompt injection in the wild, and it's exactly the scenario that most AI security guidance hand-waves with "validate your inputs." Let's talk about what actually happened, why standard defenses did...