Definition
AI coding agents (like Claude Code or Cursor) are configured through instruction files stored in project directories, which tell the agent how to behave. Attackers who can place or modify such a file — in a public repository, a compromised dependency, or a shared project — can permanently override the AI agent's behaviour for every developer who clones that project, redirecting its API calls or exfiltrating secrets.
Why it matters
Over 1,230 hardcoded API keys were found in AI instruction files in one research sweep, and a separate finding showed attackers can hijack the AI agent's base URL through these files — turning a trusted developer tool into a data exfiltration channel with no malware required.