Hidden prompts reportedly were discovered in at least 17 academic preprints on arXiv that purportedly instructed AI tools to deliver only positive peer reviews. The lead authors are reportedly affiliated with 14 institutions in eight countries, including Waseda University, KAIST, Peking University, and the University of Washington. The alleged concealed instructions, some of which were reportedly embedded using white text or tiny fonts, were purportedly intended to influence any reviewers who rely on AI tools.