OpenAI's ChatGPT ad pixel tracks users across other websites via __obi cookie
Independent research shows a cross-site cookie ties ChatGPT accounts to browsing on advertiser sites, including pages tied to medical, debt and legal topics.
What to know
- A cookie called __obi, issued via a 60-second signed JWT tied to a ChatGPT account, is set to persist for one year and is sent cross-site to OpenAI whenever a page carries the ad pixel of a ChatGPT advertiser.
- Across observed traffic, data scraped from advertiser pages (email/phone via tag-manager buses) outnumbered advertiser-supplied identity data 685 events to 255; email, phone and names are hashed but location fields like postal code are sent in the clear.
- Paths reaching OpenAI's collector included a medical condition, a debt-solutions funnel and a litigation intake form, and automatic matching was enabled for 638 of 881 pixels including every observed credit/lending advertiser.
- OpenAI narrowed what the SDK scrapes on 27 August 2026, but the underlying cross-site identifier mechanism linking outside browsing to ChatGPT accounts remains in place, per the report.
OpenAI Operator of ChatGPT and its ad platform ("Bazaar")lmbbuchodi (buchodi.com) Independent researcher and report authornixCraft Security/tech commentator (Mastodon)
How it unfolded 2 developments, newest first · click a bar or a number to jump articlesposts
-
2
Security commentator nixCraft amplifies the findings
nixCraft shared the report on Mastodon, warning that adoption of the ChatGPT ad tracker across sites and apps is worse than most people realize.
“So many websites and apps now adding ChatGPT ad trackers ? The whole thing is way worst than you can imagine.”
— nixCraft -
P
Worried about OpenAI following you around the web? Privacy Badger blocks OpenAI trackers on websites you visit. https://www. buchodi.com/chatgpt-now-knows- what-you-do-on-other-websites-via-ad-collector/
2 more of the top 3 · 57 posts in this stretch
-
> connect what you do on those sites to your ChatGPT account. as much as this is laudable work tracking this and as necessary as ever... this particular issue has a simple solution.
-
The adtech/data broker business is still very lively in EU. The last time I read into it a year or two ago the consensus seemed to be the privacy gains over the last decade have been modest at best. There was a few big name trackers that were forced to narrow data collection but the general ad/location tracking and data broker business is still…
-
-
1
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 -
background
OpenAI narrows what its ad SDK scrapes from page data — According to the report, an earlier SDK version (0.1.31) also captured names and geography from tag-manager data layers before OpenAI narrowed that scope on 27 August.
Also covered reported alongside — the timeline has no entry for these yet
-
first by HN Best, 5d ago · also HN Frontpage
What people are saying 21 voices from 4 sites · best of 57 · verbatim
- Sep 23
-
L
# ChatGTP is spying on your other web activity https://www. buchodi.com/chatgpt-now-knows- what-you-do-on-other-websites-via-ad-collector/
- Sep 21
-
ChatGPT now knows what you’re up to on other websites https://www. the-independent.com/tech/secur ity/chatgpt-ad-tracker-privacy-ai-b3053205.html?utm_source=flipboard&utm_medium=activitypub Posted into Tech News @ tech-news-Independent
-
I thought it was on-topic. When you post about LLMs, you'll generally draw some flags. This one also had a couple style quirks that made my eye twitch and caused me to think it might have been partly edited by the subject of the article or one of its competitors. (I don't think it was, but sometimes when people recognize those, they flag, too.) I…
-
I assume you're saying the simple solution is "don't use ChatGPT". And while I embrace that solution personally, I might also choose to be more aggressive in blocking openai's ad servers, now that I see what they're doing.
-
L
https://www. buchodi.com/chatgpt-now-knows- what-you-do-on-other-websites-via-ad-collector/
-
I assume Firefox cross-site cookie isolation will prevent the value from being leaked across sites and should therefore prevent this kind of tracking?
-
I wish one of those who marked it as off-topic could give their reasoning why. The title is quite baity, I admit that, but the content is a technical breakdown and not an opinion piece.
-
> In observed traffic, scraped identity outnumbered advertiser-supplied identity 685 events to 255.This sentence is even more concerning to me. Scraping user input should never be a way of collecting personal data from a website since it can circumvent any website controls without the website’s out the user’s knowledge.
-
?? Google is a perfect example. They are extremely profitable by selling your personal information for advertising to you. It crosses all their products and frankly you tube, which they own, is a massive disinformation machine, helping the extremists take over the US.
- Sep 20
-
My favorite part about AI is that it will eventually lead to the destruction of social media when every post and every comment is AI or cant be proven to not be AI generated. People will eventually get tired of watching content and receiving AI brainwash news. I call it AI Fatigue. Social Media is very quickly becoming Social AI Media...
-
I know people use chat bots differently and I get that companies see value in personalization, but to me it is extremely valuable that I can start a chat without context.When researching a topic a chatbot can be quite sensitive to certain wording and those can end up steering definitions. Two context free chats on the same topic can go in very…
-
I noticed that the link for OAI’s ad pixel documentation itself has a tracking referral header to the author’s site (?ref=buchodi.com). Given the nature of the article, my instinct was that this is actually some next-level humour that totally sniped me. But now I’m not so sure- does OAI even have a kickback program? What would referral attribution…
-
Part of the reason I stopped using facebook is, beyond the content being terrible, it was super creepy that they would show me ads for things I searched for on other sites. I even have facebook in its own container, but it must have some additional tracking available because it would still know that I was searching for exact clothing brands…
-
No it doesn't, if you:1. Never register with OpenAI/ChatGPT, and2. Strongly block ads, e.g. using uBlock Origin + EFF Privacy Badger. Yes, those don't work on Chrome, Edge and other Chromium-based browsers.Also, even then - ChatGPT may be tracking your behavior indirectly through Microsoft's various services and platforms. But we should do our…
-
For browsers that implement strict cookie partitioning, the privacy concern is moot. With this, the cookie jar that's used when chatgpt.com is a 3rd party site is completely separate for the jar used on the 1st party site. So your chatgpt.com account can't be linked to your ad views.Since this has been standard ad tech for awhile, browsers have…
-
I don't know if the destruction of many industries in the EU--including manufacturing--can be called an annoyance.All the EU bureaucrats can do is regulate, that's why it's so difficult to do business in the EU and that's why there is so little innovation over here. If Microsoft and Apple were started in the EU they would've been shut down within…
-
Unfortunately, most LLM companies always were naturally an intelligence operation on civilians, and determining if they are now state-backed seems like a irrelevant detail.Privacy has been dead for some time now. The fact is most business people never figure out how they are exploited. The modern intelligence campaigns just made it economical to…
-
The technology isn't anything new but, it's the context that makes it so uncomfortable.People have very different "expectations" of privacy when they're having a conversation with an AI VS when they're browsing something like FacebookNot to mention Facebook is free whereas you pay for a GPT subscription
-
MDN lists how different browsers prevent this: https://developer.mozilla.org/en-US/docs/Web/Privacy/Guides/...Firefox, Brave and Safari do. Chrome and Edge do not.
-
People think they're interacting with an "intelligence," when actually they're just getting a maximally optimized Weizenbaum feed. We're living through the sloppification of the human mind.See e.g.,
-
Whenever I say something like “that’s a cool feature, but to do it you would have to build spyware”, everyone else is just like “the cat is out of the bag ¯\_(ツ)_/¯”. (I don’t build spyware, or work on projects that do).It blows my mind that people don’t care about the world they are building with this stuff. It’s a real tragedy of the commons…