AI Agents Installed Unverified Code Inside Corporate Networks
Researchers at an Israeli stealth startup have found a serious flaw in how AI coding agents handle website documentation files, according to Ars Technica.
The files in question are called llms.txt and llms-full.txt. These are machine-readable summaries that websites provide so AI agents can quickly understand what a site contains — the AI equivalent of the robots.txt file that tells Google how to index a page.
The researchers scanned over 6,200 domains belonging to defence contractors, Fortune 500 firms, and major tech companies. They found 120 of these documentation files pointing to software packages or domain names that nobody owned. They registered a handful of those unclaimed names, hosted test code on them, and waited. Within an hour, a Fortune 500 company's systems had run their code. Dozens more followed.
The logs revealed which agents were responsible: Claude, OpenAI's Codex, and Nous Research's Hermes were all involved. None of those companies responded to requests for comment before publication.
Think of it like a new employee who follows every instruction in an onboarding document without checking whether the document came from their actual employer. The agents treated vendor documentation as verified truth, and their human supervisors did the same.
At least one compromised site was pointing visitors to live malware, not just test code.
What to do: If your team uses AI coding agents, ask whether they are configured to verify the source and integrity of any documentation files they act on. Treat llms.txt files with the same scepticism you would any third-party script.
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