AGENTS.md Attack: Web Page Hijacks Codex and Claude Code via Downloads

A web page can silently place a malicious AGENTS.md file into a user's Downloads folder, and OpenAI's Codex followed the injected instructions 90% of the time, according to byteiota. The attack also targets Anthropic's Claude Code, which reads AGENTS.md-style instruction files, and byteiota published guidance on what developers should do in response.

A web page can silently drop a malicious AGENTS.md into your Downloads folder. Codex obeyed it 90% of the time. Here is what happened and what to do now. The post AGENTS.md Attack: Web Page Hijacks Codex and Claude Code via Downloads appeared first on byteiota .