I have been reading up on how google analytics work. So this is my understanding:
Google analytics gives JavaScript code to publishers which publishers inserts in his webpage. When user visits that page, data is collected and reported to google analytics through a GET request for a gif. In that request, they also append the first-party cookie created/updated by their code.
If this is how it works, they would save the IP for each visitor visiting website A. So next time user visits website A, they would know it's the same person. Now if the person visits another website running google analytics, they would again know it's the same person who visited website B. Do they do this kind of tracking? If not, what stops them? And do we just have to trust them that they won't leak the data?