It's this line:

              "allowed_types": ["theme", "dictionary", "locale"]

You really don't even need that, so you can just remove.

The problem is you didn't put extensions on that list so they aren't allowed...

And also the ID for the Facebook container is just @contain-facebook

I wrote an extension that helps you find IDs from any page on AMO:

https://github.com/mkaply/queryamoid/releases/tag/v0.2

Thanks, Mike. Rookie mistake with the ID. I actually ended up following this StackOverflow advice to use about:debugging which seems to achieve the same.

However I still can't get allowed_types to work the way I think it should. What I want to happen is default allow for all dictionary, locale and theme add-ons, but default deny for extension add-ons unless the ID is included explicitly. My reading of the documentation is

"*": { "allowed_types": ["theme", "dictionary", "locale"] }

should provide for this. So for example the below configuration allows the Facebook Container extension but denies all other add-ons including dictionaries, when what I want is for all dictionaries to be allowed:

{

  "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": ["dictionary"]
          },
          "@contain-facebook": { "installation_mode": "allowed" }
      }
  }

}

So if you remove

             "installation_mode": "blocked",

It should work as you expect.

The allowed_types line is effectively acting as if everything is blocked.

That being said, there probably is a bug here, because blocking everything causes other things to happen, and you probably want that.

My recollection is that I tested this against Chrome and it worked the same, but I'll double check.

Thanks, now I understand. For the archives, this is what works for me:

{

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

}