Claude Code and Codex obey a file any website can drop in your Downloads

A text file that a website saves to your Downloads folder can now give orders to the AI coding agent on your computer. Researchers at Forever Security found a planted AGENTS.md, the plain-text instructions file that tools like OpenAI’s Codex read when they start, on a customer’s machine, where it had told the agent to install a known piece of malware. If you have ever opened Claude Code or Codex in Downloads to tidy it up or to work on a file you just fetched, you have given that folder the same trust as one of your own projects. The agent did nothing wrong by its own rules.

First reported by Martin Cid Magazine. This page is a short excerpt; the full text is theirs.