OpenAI has integrated a tracking cookie into ChatGPT that links users' online behavior to their accounts when they visit third-party websites.

A researcher known as Buchodi published a technical report analyzing the entire tracking chain of the chatbot's advertising platform, codenamed bazaar.

According to Buchodi, the advertising code for websites functions like a tracking pixel. When ChatGPT is activated, the service generates an identifier, associates it with the user's account, and stores it in a cookie named __obi for the .openai.com domain.

How OpenAI's advertising code operates. Source: Buchodi.

When a user visits a commercial website that has OpenAI's advertising pixels installed, the browser automatically sends the __obi cookie in the request back to the server.

The researcher replicated this mechanism using Chrome on Android and verified it through two independent methods. The domains involved, as per his findings, are bzr.openai.com and bzrcdn.openai.com.

During his observations, he identified 936 pixels across 1,029 hosts and recorded 23,929 requests without a query string in the URL.

What Information is Transmitted?

The solution transmits conversion events and optionally encrypted email addresses, phone numbers, names, and geolocation data down to the postal code, according to a cybersecurity expert. Hashing is performed using the SHA-256 algorithm within the browser.

The tool gathers not only information provided by the advertiser but also data from the webpage, forms, and tag management systems.

Buchodi estimated that general data collection occurred in 685 instances, while extended data transmission was noted in 255 cases. Emails and phone numbers were sent in hashed format, while country, region, city, and postal code were transmitted in plaintext.

The researcher asserted that the mechanism might also affect some unauthorized users. Out of 932 decoded sync tokens, 736 belonged to users with accounts, while 196 were associated with anonymous users.

Buchodi emphasized that the observation was limited to Chrome on Android, noting that Safari blocks third-party cookies, and all browsers on iOS utilize WebKit.

He compared this scheme to practices used by Meta and Google in their social networking platforms.

"The mechanism is standard for advertising technologies. However, its use in AI-based chat products is unprecedented. People disclose information to them that they would not share on social media," the researcher added.

It is worth noting that in February, OpenAI began incorporating advertisements into ChatGPT for adult users on the cheaper Go plan and for those without a paid subscription.