Mozilla is working on implementing patches from the Tor project in Firefox subsumed in this meta ticket. The respective wiki site says: Needless to say that this makes life for the Tor developers much easier. And privacy- and security-oriented Firefox users will be happy to enable those preferences in about:config. In Firefox v. 50 three patches are already implemented: 1. browser.download.forbid_open_with ensures that the download dialogue is no longer offered with the "open with" option. 2. Another patch ensures that navigator.plugins and navigator.mimeTypes no longer expose installed plugins. 3. A third patch ensures that screen.orientation.angle always reports 0 and screen.orientation.type always reports landscape-primary - regardless if that's true or not. Note that patches 2 and 3 are javascript objects which you won't find in about:config. In order to enable them you have to set privacy.resistFingerprinting to true.