IMDEA Networks study: trackers in all nine major AI chatbots; six web clients leak prompts, titles or screenshots to third parties
A September 2026 paper from IMDEA Networks ("Prompt like a Butterfly, Sting like a Tracker") analysed the web and Android clients of nine chatbots (ChatGPT, Claude, Gemini, Microsoft Copilot, Grok, DeepSeek, Perplexity, Mistral Le Chat and Meta AI) and found at least one third-party advertising or tracking service in every one, 44 third-party organisations in total, and 6 of 9 web and 3 of 8 Android clients sending conversation URLs, titles, prompts or screenshots to third parties, often with persistent user IDs.
Key facts
- Authors: Guilherme Oliveira, Miguel Sanchez, Roi S. Serna, Tautvydas Jackevicius, Jorge Garcia-Herrero, Aniketh Girish, Guillermo Suarez-Tangil, Narseo Vallina-Rodriguez and others (IMDEA Networks / UC3M)
- Static and dynamic analysis across consent choices, subscription tiers and access-control settings
- 44 third-party organisations; every service integrates at least one advertising/tracking service; some trackers activate only after cookie consent
- 6/9 web and 3/8 Android clients disclose conversation-derived artefacts (URLs, titles, prompts, screenshots) to third parties
- All services expose shared conversations without authentication; on Grok's sharing pages TikTok collected conversation screenshots, and Meta and TikTok collected the latest prompt
- Responsible disclosure to providers and European data-protection authorities; legal analysis under GDPR and ePrivacy
- Motivation: chatbot providers adopting ads (e.g. OpenAI's Criteo pilot for ChatGPT free tier)
What happened
The date is taken from the PDF's file name (20260916); the paper reached the Hacker News front page on Sept 29. Per-provider results are in the paper's tables and were not all transcribed here.
Why it matters
As chatbots add advertising, the ad-tech tracking stack is being attached to the most sensitive text people write. The paper documents that conversation content already reaches third parties, which gives EU regulators concrete cases.
Changelog
- 2026-09-30: created (sweep 2026-09-29, HN 404 points)
Sources (2)
- paperPrompt like a Butterfly, Sting like a Tracker: A Privacy Analysis of Web and Mobile Conversational AI Agents (PDF)
- discussionHacker News discussion (404 points, Sept 29)
id: 2026-09-16-imdea-conversational-ai-tracking-study · updated 2026-09-30 · open in the interactive timeline