Firefox now has Terms of Use! This'll go over like a lead balloon.

You give Mozilla all rights necessary to operate Firefox, including processing data as we describe in the Firefox Privacy Notice, as well as acting on your behalf to help you navigate the internet. 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.

https://www.mozilla.org/en-US/about/legal/terms/firefox/

Update: See below in the thread for their clarification.