Developers will still be free to self-distribute extensions on the web, and users will still be able to install self-distributed extensions. With this change, we are enforcing more transparency in the installation process, by letting users choose whether they want to install an application companion extension or not, and letting them remove it when they want to. Ever since we implemented abuse reporting in Firefox 68, the top kind of report we receive by far has been extension installs that weren’t expected and couldn’t be removed, and the extensions being reported are known to be distributed through sideloading. November 1 update: we’ve heard some feedback expressing confusion about how this change will give more control to Firefox users. To give users more control over their extensions, support for sideloaded extensions will be discontinued. This mechanism has also been employed in the past to install malware into Firefox.

Sideloaded extensions frequently cause issues for users since they did not explicitly choose to install them and are unable to remove them from the Add-ons Manager. This installs the extension in all Firefox instances on a computer.

Sideloading is a method of installing an extension in Firefox by adding an extension file to a special location using an executable application installer.

I want to uninstall mozilla firefox