Firefox and Thunderbird install an optional service called the Mozilla Maintenance Service which allows application updates to occur in the background, without requiring you to click Yes in the Windows User Account Control (UAC) dialog.

How does the Mozilla Maintenance Service work?

When Firefox or Thunderbird downloads an application update, the Mozilla Maintenance Service gets permission from Windows to allow the update to be applied, without requiring you to click Yes in the Windows User Account Control (UAC) dialog. Until that time, the service doesn't run so it doesn't use any computer resources and, once the update process begins, the service quits. Want more technical details? See this Mozilla Wiki page.

Disabling the Mozilla Maintenance Service

If you'd like to be prompted to authorize updates, you can disable the Mozilla Maintenance Service as follows:

Firefox

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Click the General panel.
3. Scroll down to Firefox Updates. (Tip: You can also search for updates in the search box.)
4. Uncheck the box next to Use a background service to install updates.

Thunderbird

1. In the menu bar, click the Thunderbird menu and select Settings.Click the menu button and choose Settings.
2. Click the Advanced panel.
3. Click the Update tab. The update options are displayed.
4. Uncheck the box next to Use a background service to install updates.
5. Click OK to save your changes and close the Options window.

Uninstalling the Mozilla Maintenance Service

You can uninstall the Mozilla Maintenance Service from your computer if you wish.

• Windows 7: See Microsoft's article, Windows 7 – How to properly uninstall programs.
• Windows 8: See the Microsoft Community forum thread, How do I delete or uninstall a program in windows 8.
• Windows 10: See Microsoft's article Uninstall or remove apps and programs in Windows 10.