This add-on allows to manage preferences from windows registry. You can then use Group Policies from Microsoft Active Directories to manage Firefox preferences.
To use this add-on you will need an additional adm file to define the registry keys that GPO for firefox add-on will read.
Currently the add-on will read its preferences from HKLM or HKCU \Software\Policies\Mozilla\LockPref for locked settings and HKLM or HKCU \Software\Policies\Mozilla\defaultPref for normal users preferences.
You can find an adm file ready to be used for your GPO at the following link
How this extension works: When Firefox is launched the main function reads registry and writes preferences. There is no registry observer to update preferences while Firefox is running. adm file is an administrative template that is used to build Group Policy Objects in Microsoft Active Directory. Loading this adm file allows administrator to centrally define registry setting and deploy them to groups of users and computers. Active Directory will then write the registry according to the location defined in the .adm file.
So this is a 2 step process. Use the .adm file to build a GPO that will write the registry settings for Firefox on end user computer, then use the extension to read these settings and write Firefox preferences.
The extension also contains a function that will disable the "Check for Update" menu item from Help Menu if "app.update.enabled" preference is set to false so you can keep all your computers to the same version of Firefox and make sure your environment is stable.
Since version 0.9.4 we removed the ability to hide this GPOFirefox from the extension list due to the Mozilla extension policy. Try to install this add-on at a location where the user doesn't have the rights to uninstall it (programs folder on Windows 7). Maybe we can bring this feature back in a future version, but for now we had to remove it to get a successful review by Mozilla.
https://addons.mozilla.org/it/firefox/addon/gpo-for-firefox/