With version 52 of Mozilla Firefox released, the default installation has disabled support for NPAPI plugins.
This means you will no longer be able to administer Microsoft Intune via the Firefox browser.
Thankfully, Mozilla do have an Extended Support Release (ESR) version. So to continue to use Mozilla Firefox to manage Microsoft Intune Silverlight, we suggest installing the ESR version rather than running an out-of-date browser.
To install the ESR version, download the localized version from here
Over the next few months we’ll be migrating away from Silverlight to the Intune Azure Portal, so the Silverlight plugin requirement will go away shortly.
Senior Service Engineer
Enterprise Client and Mobility – Intune