Mozilla intends to remove support for most NPAPI plugins in Firefox by the end of 2016. This decision mirrors actions by other modern browsers, such as Google Chrome and Microsoft Edge, which have already removed support for legacy plugins. Adobe Flash is still a common part of the Web experience for most users, Mozilla will continue to support Flash within Firefox as an exception to the general plugin policy. The Web provides an increasingly rich environment which should eliminate the need for plugins, and we are eager to continue improving the Web platform for use cases where plugins may still be required.”]
Source: https://blog.mozilla.org/futurereleases/2015/10/08/npapi-plugins-in-firefox/