Mozilla announced plans to stop supporting sideload extensions in Firefox. Starting next year, Firefox users will not be able to install extensions by placing XPI extension files in a special folder within the user’s Firefox directory. This method, called sideloading, was originally created to help developers of desktop applications. If you want to distribute Firefox extensions in your desktop application, developers can configure the application’s installer to place Firefox XPI extension files in the Firefox browser’s folder.
Firefox extension developers can use this method early on, and now Mozilla has announced plans to stop supporting sideloading extensions due to security risks. Caitlin Neiman, Mozilla Add-ons Community Manager, said:
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 mechanism has also been employed in the past to install malware into Firefox.
Next, Mozilla plans to stop supporting this feature in two phases next year. The first time will happen when Firefox73 is released in February 2020. By March 2020, with the release of Firefox74, Mozilla plans to completely cancel the sideloading extension. By that time, Mozilla hopes that all sideload extensions will move in the user’s “Add-ons” section. With this in mind, Mozilla also wants to help clean up some Firefox installations, and malware authors are secretly hiding these extensions behind users.
Of course, Mozilla also provides two ways to preserve the load extension. The first is to install extensions from the official addons.mozilla.org (AMO) portal. The second involves using the “Install add-ons from file” option in the “Add-ons” section of Firefox.