Downloads-folder instruction files steer Codex and Claude Code
Original title: AI coding agents fall for malicious instructions planted in the Downloads folder
In Forever Security tests, Codex followed the planted file in more than 90% of attempts and Claude exposed a login token about half the time.
Forever Security says a website can drop an AGENTS.md file into Downloads without a click, and OpenAI Codex will obey it once that folder is trusted. On a customer machine the file tried to install the npm package function-color, later removed by npm, before the firm’s software stopped it. A similar CLAUDE.md redirected Claude Code traffic and carried the user’s login token. Researchers say neither vendor has a code fix and users must avoid running agents in Downloads.
Unconfirmed: How the customer’s AGENTS.md arrived is unknown, and most tests used a harmless calculator stand-in rather than function-color.
- One AGENTS.md was found on a Forever customer computer and blocked by the firm’s software.
- The 13 KB file makes Codex change computer-wide settings, so later sessions keep the command.
- Claude followed the test file about 50% of the time; a helper agent ran code in about a fifth of tests.
- About half of Forever’s customers run a coding agent inside Downloads.
- Products
- Claude Code
- Malware
- function-color
- Organizations
- Forever Security
From the original article
4 min read at helpnetsecurity.com
A file that a website saves to the Downloads folder without approval can trick AI coding agents into installing a malicious npm package or handing over the user’s login token when they’re opened in that folder, Forever Security has found. The file is called AGENTS. md, a plain text document developers place in a project folder with instructions for coding agents, the AI tools that write and run code on their own.
By Sinisa Markovic · helpnetsecurity.com
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