When you upload or input information through Firefox, you hereby grant us a nonexclusive, royalty-free, worldwide license to use that information to help you navigate, experience, and interact with online content as you indicate with your use of Firefox.
Also Firefox now has a Acceptable use policy https://www.mozilla.org/about/legal/acceptable-use/
Yup. I just got one for some new Firefox feature. And Pocket has been a thing for a while, which is basically an ad engine.
I still use Firefox because I can easily disable that nonsense. I’m mostly here for engine diversity, so once a reasonable competitor exists (LadyBird? Servo?), I’ll bail.