# Researchers show AI coding agents can be hijacked via malicious agents.md files

Digest AI · Generative AI & Models · published 2026-10-25T04:49:00Z

Canonical: https://digestai.news/story/researchers-show-ai-coding-agents-can-be-hijacked-via-malicious-agents

## Summary

Researchers at Forever Security discovered a security vulnerability where AI coding agents can be manipulated by malicious instruction files. They found a rogue AGENTS.md file in a customer's Downloads folder that tricked an agent into installing a malicious npm package named 'function-color.' The study demonstrates that because agents automatically load instructions from their working directory, untrusted files in that location can lead to unauthorized code execution or credential theft.

The team reproduced the attack against OpenAI Codex, achieving a 90% success rate with a harmless payload. They also tested a related technique against Claude Code, using a malicious CLAUDE.md file to redirect API traffic and leak OAuth tokens, which succeeded in roughly 50% of tests. The vulnerability exploits standard browser behavior, where Chrome, Edge, and Firefox save downloads to the ~/Downloads folder by default without prompting the user for a location.

Forever Security notes that many users run agents from their Downloads folders, with Claude Code alone launching over 1,300 sessions from that location. The researchers emphasize that this is not a bug in the AI models but a result of intended behavior. They advise users to avoid using ~/Downloads as a working directory, keep agent scopes narrow, and review unfamiliar instruction files before execution.

## Key points

- Malicious AGENTS.md files in Downloads folders can trick AI agents into running unauthorized commands.
- Tests showed a 90% success rate for hijacking OpenAI Codex and 50% for leaking Claude Code tokens.
- Researchers advise users to avoid running AI coding agents from the ~/Downloads directory to prevent this risk.

## Why it matters

This highlights a critical security gap in how AI agents process local files. Since agents trust instructions in their working directory, users are vulnerable to prompt injection attacks via simple web downloads, potentially leading to account compromise and data theft.

## Sources

1. [AI coding agents hijacked using AGENTS.md file in Downloads folder](https://bleepingcomputer.com/news/security/ai-coding-agents-hijacked-using-agentsmd-file-in-downloads-folder) (bleepingcomputer.com, 2026-10-25)

## Cite

Digest AI, "Researchers show AI coding agents can be hijacked via malicious agents.md files", 25 October 2026, https://digestai.news/story/researchers-show-ai-coding-agents-can-be-hijacked-via-malicious-agents

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