In Firefox 48, Mozilla will enable a new Firefox plug-in blocklist by default. Initially the blocklist will be small, mostly containing URLs of Flash SWF files that have been identified by Mozilla as supercookies (i.e. cookies that are very hard to shake off) or fingerprinting files (i.e. they scan your system and create a unique fingerprint, again usually for tracking purposes).
Firefox 48, due out on August 2, will also be the first time that Electrolysis (splitting Firefox into a content process and a UI process) will be rolled out to the masses.