@parker @feld @MK2boogaloo I will say that it is not supposed to be possible. However there have been side-channel attacks where for example, you could put a tracker on your site that makes requests to other sites. the javascript can't read the response but you can time the request somehow, and based on the timing you can determine if it was probably in the user's browser cache already and that tells you they had been to that site before. I don't know if that is still possible but it had been done in the past.