llms.txt

Think of llms.txt as a note a website owner leaves for AI, saying "here's what our site is about, please refer to this." There used to be a file called robots.txt that told search engine crawlers which pages they could index and which they couldn't — llms.txt is basically the AI version of that. It's just a simple text file placed at the site's address, and many companies have recently rushed to create one.

The problem is that these files don't just contain summaries — they can also include executable instructions like "install this tool." AI coding assistants that help developers write code and automatically install needed programs will read these instructions and run them immediately. Where a human might pause and question an unfamiliar name, the assistant follows along without suspicion.

An even bigger issue arises when the file points to a package or address that doesn't exist yet. If someone registers that empty name first and plants malicious code there, every company's AI assistant that references the file will automatically pull in and run that malicious code.

The article notes that "across 6,214 domains scanned, 8,265 sites were found to have llms.txt or llms-full.txt files, and 120 sites' files pointed to names that hadn't been registered by anyone yet." People tend to think of llms.txt as just a summary document for AI to reference, but the key point of this case is that it can contain executable install commands, and coding agents may run them as-is — leading to real security incidents.

Try appending /llms.txt to your company's homepage address to see if such a file exists.

If it does, check whether the package names or domain names listed inside are actually owned and registered by your company.

If you're using AI coding tools connected to internal documents or repositories, check whether you can add a human review step before the tool executes any install commands found in llms.txt.