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
ChatGPT doesn’t know shit about me since I’ve never used it.