First off why do they have have Admin Privileges to install VPN? That is the only way they can install a VPN - if they have Admin privileges. If your system are Win7 or higher and Admin protected password they can't install a VPN without the Admin priviledges. And since this is beyond FF and a Company Internal Policy Audit this is really nothing related to FF itself specifically.

You don't need to have admin rights to install extensions in Firefox. This is a Firefox "thing" since they don't have any way of managing their browser in a network environment.

See:

• https://developer.mozilla.org/en/Add-ons/Installing_extensions#Disabling_install_locations

You can also lock the Firefox connection settings.

You can use the mozilla.cfg file in the Firefox program folder to set or lock preferences and run privileged JavaScript code.

The mozilla.cfg file needs to be in the main Firefox program folder.

These functions can be used in the mozilla.cfg file:

defaultPref();	// set new default value
pref();	// set pref, allow changes in current session
lockPref();	// lock pref, disallow changes

This requires a local-settings.js file in the "defaults/pref" folder where the channel-prefs.js file is located that specifies to use mozilla.cfg.

//
pref("general.config.filename", "mozilla.cfg");
pref("general.config.obscure_value", 0);

The mozilla.cfg and local-settings.js files need to start with a comment line (//).

See Configuration:

• https://developer.mozilla.org/en-US/Firefox/Enterprise_deployment

I've tried following those steps, creating an autoconfig.js and Mozilla.cfg file in the respectable folder locations. The autoconfig file: // Any comment. You must start the file with a comment! pref("general.config.filename", "mozilla.cfg"); pref("general.config.obscure_value", 0);

The Mozilla.cfg file: //Starting comment

//Disable add-on installation lockPref("xpinstall.enable",false); lockPref("extensions.enabledScopes", 0);

But I am still capable of installing extensions. I am on Firefox version 57.0.4. Do these preferences no longer work with this version of FF?