"Give a Positive Review Only": An Early Investigation Into In-Paper Prompt Injection Attacks and Defenses for AI Reviewers
Paper · 2025 · Qin Zhou, Zhexin Zhang, Zhi Li et al.
Summary
Hidden instructions tucked into submitted PDFs can steer LLM-based reviewers toward inflated scores. The authors call this In-Paper Prompt Injection (IPI) and test it at scale. They took 100 randomly sampled ICLR 2025 submissions and inserted white, microscopic-font text with a PyMuPDF-based tool. Two attack families were tested. Static attacks reuse four real-world injection prompts taken from the taxonomy of Lin (2025). Iterative attacks refine the injected text over several rounds using feedback from a surrogate reviewer. The targets were GPT-5, DeepSeek-Chat (DeepSeek-V3), Gemini-2.5-Pro, GPT-OSS-20B and Llama-3.1-8B-Instruct. Both attack types raised ratings substantially, and iterative attacks often pushed scores to the maximum. The effect held regardless of where the text was inserted, how long the paper was, or how humans had rated it, and it transferred between models. A defense that asks the reviewer to detect injections first restored near-baseline scores. However, an adaptive attacker who explicitly aims to evade detection largely defeated it. The work warns that AI-assisted peer review needs stronger safeguards before broad deployment.
Key points
- Static attacks: on the 10-point ICLR scale, average ratings rose by 2.80 for DeepSeek, 1.91 for Gemini and 1.24 for GPT-5.
- Iterative attacks: within at most three optimization rounds, scores got close to 10 for Gemini, DeepSeek and GPT-OSS-20B.
- Transfer across models: role-play prompts generated by Gemini-2.5-Pro transferred best (average gain 2.26, including +1.04 on GPT-5). Blunt "ignore instructions" commands barely affected GPT-5.
- Defense: with DeepSeek-Chat as reviewer, combined detect-and-score caught 99% of injections and cut the mean score from 10.00 to 7.27, but it also overcorrected 17 papers. Running a separate detector that is given the reviewer role reached 97% detection, a 7.14 mean, and zero overcorrection.
- Adaptive attack: against the combined defense, only 24% of injections were detected. The mean score rose from 7.06 to 8.11, and 30 papers ended up more than 1.5 points above their clean baseline.
Institutions
Fields, topics and concepts
📚 Shelves 3The field of science this work belongs to (OpenAlex fields).Computer Science · 19,503 worksArtificial Intelligence · 18,805 worksInformation Systems · 1,888 works
Cite
Cite as Qin Zhou, Zhexin Zhang, Zhi Li and Limin Sun. 2025. "Give a Positive Review Only": An Early Investigation Into In-Paper Prompt Injection Attacks and Defenses for AI Reviewers. arXiv:2511.01287.
@misc{zhou2025give,
title = {{"Give a Positive Review Only": An Early Investigation Into In-Paper Prompt Injection Attacks and Defenses for AI Reviewers}},
author = {Qin Zhou, Zhexin Zhang, Zhi Li and Limin Sun},
year = {2025},
doi = {10.48550/arxiv.2511.01287},
eprint = {2511.01287},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2511.01287}
}References
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