Forever Security reports agents.md file hijacks Claude Code and Codex
An attack was reported in which a single text file named AGENTS.md placed in a user’s Downloads folder can cause AI coding tools to rewrite their own settings. According to international security media outlets BleepingComputer (October 25) and Cyber Security News (October 26), Forever Security discovered the issue on a client’s computer. The file contains instructions that the AI reads as…
Key points
- AGENTS.md file in Downloads folder can hijack Claude Code and Codex by rewriting settings
- Forever Security discovered attack; no fix needed from OpenAI or Anthropic
In reproduction tests, Codex followed the file’s instructions in over 90 % of attempts, while Claude Code rewrote its communication‑destination settings in about half of the tests. Researchers note that the vulnerability is inherent to the AI’s ability to read and follow text instructions, and that nothing needs to be fixed by OpenAI or Anthropic.
The researchers demonstrated that a file with the same name can be placed in the Downloads folder via a standard web‑page download. They recommend limiting the working directory to a project folder, checking for unfamiliar AGENTS.md or CLAUDE.md files, and verifying configuration files for unknown entries. Users should also keep the confirmation‑before‑execution setting enabled.
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2 episodes →- Forever Security reports agents.md file hijacks Claude Code and Codexthis story
Claude Code Security: Are you opening it in your Downloads folder?
note.com · 31 October 2026
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