In a very odd move Mozilla has made a change to the latest Firefox Nightly (Firefox 42) Win64 which only allows the Shockwave Flash NPAPI plugin. Note: the Prime Content Decryption and Open H264 are now standard all will always be supported.
While Shockwave Flash is still supported Silverlight is not. Simple enough, just install the plugin and you’re ready to go. Users won’t be able to install Silverlight in the Win64 version of Firefox since it is not allowed. Microsoft’s Silverlight is used by Netflix and Amazon Video along with many other Video on Demand (VOD) sites (especially outside the US).
This is a result of Bug 1165981 which originally when created in May 2015 was suppose to be Flash and Silverlight.
Firefox 64 bit will launch with highly restricted access to NPAPI. The requirement here is to create a whitelist so that the only allowed NPAPI plugins are Flash and Silverlight.
Without much explanation Silverlight was removed from NPAPI Whitelist in early July 2015. Silverlight will still be available in the 32-bit builds of Firefox. Interestingly, Microsoft has removed support for Silverlight from The Edge (Windows 10) browser, but still supports it in Internet Explorer.
Restricting the access to NPAPI is a good security move. However, it does not make sense to still allow access to the biggest security risk which is Flash and disallow Silverlight. Yes, Silverlight has had its fair share of security problems, but nowhere as much as Flash. The only explanation I can think of is Mozilla did not want to block users from Facebook which is still heavily Flash. Though Facebook CSO wants ‘End of Life Date’ for Flash
On a side note, Bug 1187005 was filed shortly after this landed calling this change a regression. It will be interesting to see how this plays out.
ETA: It was brought up in the mozillaZine Firefox Builds forum that this would also disable support for Java and Unity Player (which Chrome already did in April, but can still be re-enabled). Also I forgot to include this rather disturbing comment on the bug from Benjamin Smedberg [:bsmedberg]:
What we want here is for the plugins to not even be detected at all, not show up in the addon manager, and not be user-enablable or even programmatically with an extension.
This completely goes against everything Firefox was about when it first came out. Firefox is moving from an OpenSource browser to a nanny browser as it seems Mozilla thinks it knows what it is best for their users.