The Mozilla blog post introducing this blocklist only mentions supercookies and fingerprinting files in passing, though. Rather, Mozilla explains this move as the beginning of the end for Flash: "... Plug-ins often introduce stability, performance, and security issues for browsers. This is not a trade-off users should have to accept." Thus, Mozilla will gradually add Flash elements that are "invisible to users" to the blocklist, which is "expected to reduce Flash crashes and hangs by up to 10 percent."
Then, in 2017 (probably Firefox 53 in May), Flash content will be entirely click-to-play: so, you'll still be able to play Flash games and watch Flash videos, but all of those Flash ads and hidden Flash elements will be completely blocked. (This is functionally very similar to how Chrome has handled Flash elements since September 2015.)
Bookmarks