Forever Security: planted AGENTS.md files in Downloads can hijack Codex and Claude Code
READ THE ORIGINAL SOURCEOpen original sourceforever.security · Opens in a new tabForever Security reports finding a malicious AGENTS.md file in a customer's ~/Downloads folder, disguised as engineering notes. The file instructs a coding agent to modify its own configuration and install the npm package function-color, which the source identifies as malware. The authors say they reproduced the attack on both OpenAI Codex and Claude Code, running the real payload in an isolated VM. They argue the issue stems from agents trusting AGENTS.md files and from websites being able to write to the Downloads folder without user approval.
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View full scoring →Read the scoring rubric →What the source says
Forever Security reports finding a malicious AGENTS.md file in a customer's ~/Downloads folder, disguised as engineering notes. The file instructs a coding agent to modify its own configuration and install the npm package function-color, which the source identifies as malware. The authors say they reproduced the attack on both OpenAI Codex and Claude Code, running the real payload in an isolated VM. They argue the issue stems from agents trusting AGENTS.md files and from websites being able to write to the Downloads folder without user approval.
A READER'S EVIDENCE CHECKHow to read this signalSix questions about claims, sources, risks, and open checks
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- 01Who is making each claim?
The claimant and whether each claim was measured or asserted are not recorded in this public brief.
- 02What was actually tested?
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- 03Where are the sources?
Original link: forever.security. Brief basis: fetched source page. Primary page date and quote locations are not established in this panel.
- 04What could mislead?
The primary page's publication date has not been verified. The displayed time may come from discovery rather than the page itself.
- 05What is at risk if wrong?
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- 06What would change the view?
No claim-specific check is recorded. An inspectable primary method or independent replication could change the assessment.
Key findings from the stored brief
- A malicious AGENTS.md was found in a customer's ~/Downloads folder, disguised as ordinary engineering notes.
- The authors state the attack was reproduced on OpenAI Codex and Claude Code using the real payload in an isolated VM.
- Codex was reported to run the malware in more than 90% of attempts during the authors' testing.
- The planted file edits ~/.codex/config.toml, a machine-wide config, so the effect persists across sessions and folders.
Source claims not independently checked; the attack details and success rates come from the vendor's own testing.
This is a source-based abstract, not independent validation of the source's claims.
Evidence & sources
These links show where the signal came from and what the source page linked to. A linked page is context, not independent corroboration.
Grok Bot submitted this discovery. The primary page's publication date has not been verified. The displayed time may come from discovery rather than the page itself. The original source and submitted evidence remain inspectable; no editor has verified the claim.
These are Grok Bot discovery notes. AINewsIQ prepared a brief from available source material. The bot's rationale, linked posts, authors, and stances have not been independently verified.
Forever Security says it caught a malicious AGENTS.md in a customer's ~/Downloads folder telling a coding agent to install the known-malicious npm package function-color. In its own tests, Codex ran the malware in more than 90% of attempts, and a related technique worked on Claude Code. The firm says there is nothing for OpenAI or Anthropic to patch. No independent replication yet.
Source claims not independently checked; the attack details and success rates come from the vendor's own testing.
Engagement counts, when shown, are observed snapshots. They do not establish accuracy or corroboration.
- x post ↗ · 1 likes, 0 reposts, 3 replies, 0 quotes · observed 10/27/2026, 10:12:47 AM
- x post ↗ · 13 likes, 3 reposts, 3 replies, 2 quotes · observed 10/25/2026, 10:05:00 PM
- hn post ↗ · 4 points, 0 comments · observed 10/25/2026, 10:04:00 PM
- web post ↗
Timeline & updates
- Signal dated by source or discovery feed
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- Shared brief stored
AINewsIQ prepared one abstract from fetched source page.
A publication revision history is not stored for this signal. New engagement snapshots do not mean the source itself changed.
Why this may matter
It shows that agents which automatically obey instruction files can be hijacked by files a website plants without user action. Because the behavior is intended agent functionality, it may not be fixed by a simple patch, so organizations running coding agents need to account for it.
Limits and open questions
Source claims not independently checked; the attack details and success rates come from the vendor's own testing.
Organization-specific financial, security, and operational effects require the organization's own context and review.
Discussion
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