Can you add a configuration setting to Mozilla Firefox to disable Create New Profile, configurable in the policies.json file? (A second option but a much uglier one would be to disable being able to select a file location for a new profile. Then you could make the default profile directory write only, which would also accomplish the same thing.) (A third option would be to able to configure extensions by default upon installation in the ExtensionSettings policy.) To explain, I use LeechblockNG on Firefox on Ubuntu. Very helpful. By placing a policies.json file (see at bottom) in /etc/firefox/policies/ directory, I can create a system wide policy. I can make the LeechblockNG extension mandatory and to be installed upon every new profile creation. That all works very well. HOWEVER, there is NO way to be able to set those options in the new profile. So LeechblockNG is installed with default options (which are no blocking at all), which effectively bypasses the addon. I am also writing the author of the leechblock extension to see if there is any way to set the options for leechblock upon installation (the third option above). But I know other people have this same question, and at present, if I am correct, there is no way to block new profile creation, or the Profile Manager window in Firefox. So could you please add that option to the Firefox policies.json configuration? Something like "DisableNewProfiles": true would do it. Thanks! My current policies.json file in /etc/firefox/policies/ directory: { "policies": { "BlockAboutConfig": true, "BlockAboutProfiles": true, "PrivateBrowsingModeAvailability": 1, "DisableSafeMode": true, "ExtensionSettings":{ "*": { "installation_mode": "blocked", "blocked_install_message": "Prohibited install more extensions." }, "[email protected]": { "installation_mode": "force_installed", "install_url": "https://addons.mozilla.org/firefox/downloads/file/4374316/leechblock_ng-1.6.6.xpi" } } } }