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/
But what does that actually mean? It just sounds as vague and non descriptive as possible, which is the worrisome part legally