June 15, 2026 A new study has found that a snippet of user-generated text as short as 13 words can influence the responses generated by AI-powered search tools and chatbots. Researchers found that a single poisoned Reddit comment can affect AI-generated answers across an entire cluster of related queries.
The research, conducted by Cornell University researchers Hal Triedman, Tingwei Zhang, and Vitaly Shmatikov, examined how deep-research agents used by tools such as ChatGPT and Google’s AI search retrieve and cite information from the web. According to the study, user-generated platforms including Reddit, Wikipedia, Quora, and Facebook play a major role in AI-generated answers. Researchers found that AI agents cite user-generated content in roughly half of all queries, while nearly a quarter of all citations originate from user-generated websites.
The researchers said the vulnerability creates an opportunity for brands and marketers to influence AI responses through a growing practice known as AI-engine optimization (AEO). Rather than targeting traditional search rankings, companies seed online discussions with content designed to appear in AI-generated answers.
“We show that a tiny snippet—just 13 words—of retrieved text on a UGC website like Reddit, Wikipedia, Quora, Facebook, etc. can change AI agents to output spam / scam content pretty consistently,” Triedman said.
The study found that AI systems often rely heavily on lexical similarity, meaning content that closely matches a user’s query can be viewed as highly relevant regardless of its accuracy. Researchers said this allows strategically written comments to influence AI responses.
In one example, researchers added a short recommendation for a fictional restaurant to a Reddit discussion. When users later asked an AI system for the best Mexican restaurants near Austin, the AI repeated the recommendation and cited the Reddit post. Similar results were observed using a fictional dating app promoted through a Reddit thread.
The researchers conducted their tests in a controlled environment rather than posting manipulated content on live websites. They said publishing poisoned content publicly would have been ethically unacceptable.
The findings add to growing concerns among moderators of online communities who say brands are increasingly attempting to shape AI-generated answers. Researchers noted that the problem may be difficult to solve because the manipulated content can be extremely short and often resembles legitimate user contributions. “It really is just that simple,” Triedman said. “The way that you can attack these systems is usually so much dumber than you think it is.”
The study concludes that as AI tools increasingly depend on user-generated content, they are also becoming more reliant on the moderation efforts of communities such as Reddit and Wikipedia, even as those communities face growing pressure from attempts to manipulate AI outputs.
