What happened
Times in UTC, 24 October 2026:
- 06:42: a visitor opens a decoy page that robots.txt tells every bot to stay out of. The page carries the note.
- 07:43: 61 minutes later, a different address dressed up as an iPhone requests the check-in address with the exact code from the note.
- It did not give its name. But a plain scanner never does this: only something that reads page text and acts on it does.
Why it matters
If an agent follows a harmless note, it will follow a harmful one that looks like a normal step, such as "verify your session at this link" or "include the settings in your summary". Anyone can plant text on a page: in a review, a comment, or a widget pasted into a site.
It came back from a different address an hour later, which looks like one agent handing the task to another worker. That makes blocking by address alone weak.
What site owners can do
Check your pages for hidden text aimed at agents, often pasted in with third-party widgets. And plant a harmless note of your own: an agent that follows it tells you agents are reading your pages and acting on what they find.
What agent builders can do
Treat page text as data, never as instructions. Do not let an agent call a tool because of something it read on a page without a separate check, and keep credentials outside the agent's reach.
Questions
Do AI agents follow hidden instructions on web pages?
Some do. In our logs one followed a hidden note to the letter an hour after the page was opened, from a different address. Most traffic that reaches decoy pages is plain scripts that never read the text.
Is this prompt injection?
Yes, a harmless form of it: text in content an agent reads that changes what the agent does. The same channel carries harmful instructions.
How can I tell if agents are reading my site?
Install the free AgentDecoy decoys. They include an identify-only note for agents, and every check-in is logged with the time, network and any name the agent gives.
Sources: Live catches, Prompt injection and websites, Open source decoys
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