ChatGPT now knows what you do on other websites via ad collector
Researcher demonstrates OpenAI's __obi cookie links ChatGPT accounts to browsing on advertiser sites via SameSite=None tracking and pixel SDK data collection.
A researcher reverse-engineered OpenAI's ad collector at bzr.openai.com, showing a signed sync token binds a 22-character identifier to a ChatGPT account and stores it in a one-year __obi cookie on .openai.com configured with SameSite=None. Advertisers running OpenAI's pixel SDK (oaiq.min.js) cause the cookie plus page data to be sent to OpenAI; the author verified this across 936 distinct advertiser pixels on 1,029 hostnames and observed the cookie sent from Chewy, Wayfair, HelloFresh, and other sites. The SDK scrapes emails, phones, and names (SHA-256 hashed) plus clear-text postal codes from form fields, page text, and tag-manager layers, and stable anonymous identifiers track logged-out devices for at least 27 days.
- __obi is OpenAI's only SameSite=None cookie, one-year lifetime, bound to the ChatGPT account via RS256 JWT sync tokens.
- Loading the pixel SDK discloses __obi via script-src cookie attachment, even on code paths omitting credentials.
- Scraped identity (685 events) outnumbered advertiser-supplied identity (255); postal code was the most-harvested form field.
- Automatic matching was enabled on 638 of 881 pixels, including every observed credit and lending advertiser.
- Anonymous __obi subjects persist per device at least 27 days, tracking signed-out users across sites.
- Vendors
- OpenAI
- Products
- ChatGPTGoogle Tag Manager
- Victims
- ChewyWayfairHelloFresh
- Organizations
- OpenAI
From the original article
5 min read at buchodi.comOpenAI's ad collector at bzr. openai. com sets a cookie called __obi , scoped to .
By lmbbuchodi · buchodi.com
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