https://www.fakespot.com/privacy-policy
Internet or other electronic network activity (e.g., browsing history, search history, information regarding an individual's interaction with an internet website, application, or advertisement, and online viewing activities)
Category of Third Parties to Whom Personal Information is Sold and/or Shared: Advertising partners, Service providers
Just a snippet of the privacy policy. There's other bad stuff too like location tracking. It's also all ran through Google analytics.
So much for a privacy respecting Mozilla