Mozilla plans to remove the Adobe Primetime Content Decryption Module in Firefox 52 Stable.
Adobe Primetime is a content decryption module that is only available for Firefox on Windows. It is designed to play back protected media streams. In other words, it is a plugin for DRM.
Firefox did download the Adobe Primetime plugin automatically since its introduction in Firefox 38. This changed only recently -- in Firefox 47 to be precise -- when Mozilla switched the download to on-demand only.
This means hat Adobe Primetime is only downloaded by Firefox when you visit a site that requires it to play back media. The change does not affect existing Adobe Primetime installations.
Firefox 52: Adobe Primetime CDM removal
Mozilla does not mention a reason for the decision in the bug listing. The one that makes sense the most is that the company enabled support for Google's Widevine Content Decryption Module in Firefox recently as well.
Support for Google Widevine was added in Firefox 47 for Windows and Apple versions, and in Firefox 49 for Linux. This means that the content decryption module supports all three major desktop platforms Firefox is offered on.
Mozilla is working on Widevine support for Firefox on Android, and plans to push out a first version soon.
Additionally, and that is probably the main reason for the decision, Widevine is also supported by Google Chrome.
Chrome does not support Adobe Primetime on the other hand, and since it is the browser that is most widely used, sites do favor Widevine support over Primetime support usually.
All major streaming sites should work fine with Google Widevine.
The "other" option that browsers have to stream protected media is through browser plugins. Firefox supports only NPAPI plugins, but support is on its way out as the Web is moving towards HTML5 and away from proprietary solutions.
While Firefox will continue to support Adobe Flash in Firefox 52 and in the foreseeable future, all other plugins will no longer be supported in Firefox 52. This includes Microsoft Silverlight, a plugin used to stream encrypted media in the past.
Firefox 52 is the new ESR version -- Extended Support Release -- of Firefox. It won't support Adobe Primetime CDM anymore just like any regular version of the web browser. (via Sören Hentzschel)
Now You: Do you make use of CDM in Firefox?