OpenAI ad collector links ChatGPT users' browsing to accounts via cookie
Security researcher buchodi published a technical report detailing how OpenAI's ad platform, internally codenamed 'bazaar', uses a cookie named __obi to track users across third-party websites and link browsing activity to their ChatGPT accounts. The mechanism involves a signed JWT synced from ChatGPT to bzr.openai.com, which sets a persistent cross-site cookie that is sent back to OpenAI when users visit sites with OpenAI ad pixels. The report, which reached the top of Hacker News, verified the behavior with independent capture methods and observed traffic across hundreds of advertiser pixels.
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OpenAI's ad collector at `bzr.openai.com` sets a cookie called `__obi`, scoped to `.openai.com`. The value is while you are on ChatGPT and tied to your ChatGPT account. `__obi` is then sent to OpenAI from ordinary websites you visit. Any company that buys ads on ChatGPT installs a small piece of OpenAI code on its own site, the same way retailers already install Meta and Google tracking code. Loading that code, sends `__obi` to OpenAI along with data about the page you are browsing. This includes products you are searching for, articles you are reading, and purchase behaviors. The bottom line is that OpenAI can connect what you do on those sites to your ChatGPT account. 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. ## How it works **Step 1. ChatGPT creates an identifier and signs it.** On `chatgpt.com`, the client
机器之心机器之心
编辑｜冷猫 让人担心的事情，还是发生了。 随着我们越来越习惯把问题交给 AI，聊天记录、工作内容、兴趣偏好，甚至一些原本只属于自己的细节，也在不断进入模型的视野。 但更坏的是，开发者已经实锤，OpenAI 还可能通过一些不那么显眼的方式，获取你在其他网站上的浏览行为。也就是说，即使你没有在 ChatGPT 里说出口，你在网页上的一些动作，也在成为它了解你的另一条线索。 这件事一经披露，已经冲上 HackerNews 热榜第三。 安全研究者 buchodi 近日发布了一份详细的技术调查报告，逆向了 OpenAI 广告平台（内部代号「bazaar」）的完整追踪链路。结论是，OpenAI 在 ChatGPT 中植入了一枚名为 __obi 的 cookie， 它能在用户访问安装了 OpenAI 广告像素的第三方网站时，将浏览行为关联回用户的 ChatGPT 账号 。 博客链接：https://www.buchodi.com/chatgpt-now-knows-what-you-do-on-other-websites-via-ad-collector/ 一颗 cookie 的旅程 整个追踪机制分三步完成。 第一步 ，当用户打开 ChatGPT 时，客户端生成 16 字节的随机标识符，并通过 POST /backend-api/bazaar/obi/sync-token 接口获取一个 RS256 签名的 JWT。这个 token 把随机标识符和用户账号绑定在一起，有效期 60 秒。 第二步 ，客户端将 JWT 跨站发送到 bzr.openai.com/v1/obi/sync，服务器返回一个 cookie：__obi。该 cookie 设置了 SameSite=None; Secure，有效期一年。这意味着它被明确设计为可以在跨站请求中发送。 第三步 ，当用户访问安装了 OpenAI 广告像素的商业网站时，浏览器会自动把 __obi 带在请求中发回 OpenAI 服务器。研究者在实际抓包中发现了三类请求都携带了该 cookie，其中最值得注意的一类是：浏览器加载广告像素 SDK 的 <script src> 请求本身就会附带 cookie，甚至在 OpenAI 的任何代码执行之前，标识符就已经被传回了。 简单来说： 你只要打开一个安装了 OpenAI 广告代码的网页，OpenA
