It might as well be.
To include something to your list....as of version 40, Firefox sends metadata of your browsing and downloads to Google. To protect you from unwanted software downloads. (1)
Now if its actually something you don't want to browse or download, or something some corporate entity doesn't want you to browse or download, who's to say? Why, Google of course.
All this information about you will no doubt be carefully archived by Google, cross-referenced with everything else it has on you, and added to its pool of information on you where it will remain forever.
Considering you can end up in jail for using Windows 10 (2), I don't think Firefox goes quite that far. YET. Maybe they're saving that goodie for version 50.
You cannot get away.
(1)
https://www.mozilla.org/en-US/firefo.../releasenotes/
(2)
Windows 10 is spying on almost everything you do ? here?s how to opt out | BGR