Effective in March 2017, Mozilla Firefox is removing support for Silverlight in version 52.
Microsoft is recommending that you use IE 11 for Silverlight support or earlier versions of Mozilla than 52.
Details: found HERE.
Some Applications that still are using Silverlight:
Microsoft Intune (Admin Console): This is to be transitioned into the Azure portal in 2017.
Older Versions of Service Manager Web Portal. (Update to newer versions and this will utilize HTML5).
Note: Silverlight is being deprecated due to security risks with browser plug-ins.