I am visiting mymother who likes to eat in a local supermarket where they have a cafe. I paid for our meal using cash and I did not use the in store wifi and did not interact with any in store services. I get back to my mothers apartment and open firefox to do some browsing, the first thing I see is a sponsored ad for the supermarket I have just been in. So two questions, I understand that my phone number can become visible if I interact with a local service. But no interaction took place but they still worked out who I am and where I was. How was this done? Secondly some financial interaction has presumably taken place between firefox and whoever controls the advertising for the supermarket. So they put out some kind of call to say "this guy has just been in our supermarket and we want to hit him with some linked content" and firefox have put up there hand and said "yep we got him right here, you pay us x and we will stick a link on his opening page" So how does that work with firefox? so they say thay are a privacy web brower but they appear to have just sold me off to a supermarket?