Researchers have been sneaking secret messages into their papers in an effort to trick artificial intelligence (AI) tools into giving them a positive peer-review report.

The Tokyo-based news magazine Nikkei Asiareported last week on the practice, which had previously been discussed on social media. Nature has independently found 18 preprint studies containing such hidden messages, which are usually included as white text and sometimes in an extremely small font that would be invisible to a human but could be picked up as an instruction to an AI reviewer.