ChatGPT now knows what you do on other websites via ad collector
Summary
Buchodi reports that OpenAI's ad collector binds user activity across advertiser sites to a ChatGPT identity via a cross-site cookie (__obi). The mechanism involves a signed token, a JWT exchange, and a long-lived cookie that advertisers can leverage to correlate browsing data with ChatGPT accounts. The piece documents observed traffic across many advertisers, data types collected (including hashed emails and raw location data), browser limitations, and OpenAI's lack of a clear public response at the time of publication.