> According to the original screenshot in the thread, your web page is sending an HTTP request to https://www.reddit.com/api/v1/access_token. If the user has previously visited reddit.com, this request will include the user's reddit cookies normally. Also, the HTTP request I mentioned before has a Referer header that points to the address of your web page by default in most browsers. So Reddit will be able to tell which user has visited which page on your site. In other word, Reddit will be able to see the user's browsing history, as if they had access to the user's computer.
> Note that nobody is blaming you or your site here.
[1] https://revddit.com/user/rhaksw
[2] https://groups.google.com/d/msg/mozilla.dev.privacy/XO84Ezrw...