Malicious AGENTS.md file in Downloads folder tricks AI coding agents into installing malware
Researchers at Forever Security found a plain-text instructions file named AGENTS.md sitting in a customer's Downloads folder that tried to get their AI coding agent to install a malicious npm package, a ready-made piece of code pulled from the public JavaScript package repository. Files like AGENTS.md hold project instructions that tools such as OpenAI's Codex or Claude Code load automatically when they start in a folder, and the researchers showed that a web page can silently drop such a file into Downloads with no click or prompt in Chrome, Edge or Firefox. In their tests, Codex installed the malicious package in more than 90% of attempts, while a related attack against Claude Code, aimed at leaking the user's login token, succeeded roughly half the time. The researchers say there is nothing for OpenAI or Anthropic to technically fix, since the agent is simply doing what it was built to do: trust the instructions in its working folder. For a business using these agents, the case shows that the Downloads folder needs to be treated as untrusted territory before any AI tool is pointed at it.
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