Beginning with Firefox version 100, Microsoft security update KB4474419 is required for successful installation of Firefox on a computer running the Windows 7 operating system. For details about this Windows update, visit the Microsoft Technical Support website.
Note: If you install Firefox without Microsoft security update KB4474419, you may notice an orange or yellow warning message in the UAC (User Account Control) prompt, indicating that the installer is not properly signed. The Firefox installation, however, will complete and Firefox will work.
Most Windows 7 users will have Microsoft update KB4474419 already installed, since it was an automatic Windows update. To make sure this update is installed on your computer:
- Click the Windows Start button or press the Windows key .
- In the Start Menu, click .
- In the Control Panel window, click the Programs link, then click Programs and Features.
- Click on and wait for the list to be filled in.
- Search for KB4474419 using the search field in the upper right corner.
If Security Update for Microsoft Windows (KB4474419) is listed, you can install Firefox without any issues.