Firefox 43 came out just a few days ago and with it a new security feature that Firefox had already introduced to its beta channels made its way to the stable release. As of version 43, unsigned add-ons can no longer be installed. The move is meant to prevent unsuspecting users of accidentally installing malicious add-ons from somewhere outside the Firefox market place. Mozilla’s intentions are no doubt noble but most users aren’t happy with the change. Install Unsigned Add-ons is a Firefox add-on that will let you install unsigned add-ons. It doesn’t block Firefox’s initial attempt to warn you against potentially installing an untrustworthy add-on, however, once you explicitly click the ‘allow’ button, you are able to install the add-on.
When you install an unsigned add-on in Firefox 43, you see the following pop-up. Clicking ‘Allow’ isn’t helpful since it still doesn’t let you install the add-on. Perhaps there are exceptions when it does work but for the most part, it does nothing.
Once you install Install Unsigned Add-ons, you will see the initial warning sign. After you click the ‘Allow’ button, a second warning with an install option will pop up. Click it and the add-on will be installed.
Install Unsigned Add-ons also lets you check for and enable add-ons that Firefox 43 might have disabled when you upgraded the browser. Unfortunately, the add-on pops up a box asking if you want to check for disabled add-ons every single time you open Firefox which is beyond annoying.
It’s probably best to enable the add-on only when you need to install an unsigned one. That way you can still take advantage of the security check that Firefox has added.