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OpenAI's ChatGPT ad pixel tracks users across other websites via __obi cookie

Researcher details ChatGPT's cross-site __obi tracking cookie

A report on buchodi.com, cross-posted to Hacker News, describes how chatgpt.com issues a 60-second JWT that is exchanged for a one-year __obi cookie sent cross-site to bzr.openai.com by advertiser pixel code, tying outside browsing to ChatGPT accounts; the author says findings were reproduced on-device and cross-checked against traffic from 936 advertiser pixels across 1,029 hostnames.

“I reproduced the full mechanism on my own phone, verified with two independent capture methods, and cross-checked against several months of observed traffic covering 936 distinct advertiser pixels across 1,029 hostnames.”

buchodi.com report author

OpenAI Operator of ChatGPT and its ad platform ("Bazaar")lmbbuchodi (buchodi.com) Independent researcher and report authornixCraft Security/tech commentator (Mastodon)

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Sep 21Sep 22yesterdaynow · 12:40 PM ET

Reported in the same hours no headline names this development itself — these 1 claim were published in its stretch

  1. first by HN Best, 4d ago · also HN Frontpage

All 2 developments of OpenAI's ChatGPT ad pixel tracks users across other… →

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