Firefox for Enterprise Community Forum

We're exploring adopting a default deny policy for Firefox extensions in our enterprise. However when I tested this by creating a custom policies.json Firefox unexpectedly removed all extensions for me, including the ones I thought I had allow listed. Here is my policies.json but just keeping in the Facebook Container add-on to illustrate:

{

   "policies": {
       "ExtensionSettings": {
           "*": {
               "blocked_install_message": "Only approved Firefox extensions can be installed, please email your request to itdept@example.org",
               "installation_mode": "blocked",
               "allowed_types": ["theme", "dictionary", "locale"]
           },
           "@contain-facebook.xpi": { "installation_mode": "allowed" }
       }
   }

}

What I would like is to to allow pre-approved extensions (including if they already are installed) and all other types of add-on, but remove and prohibit installation of unapproved extensions.

Can anyone assist, please?