Almost a year ago Firefox introduced a very useful feature which screened for add-ons that had been installed by third-party software and disabled them unless the users wanted to keep them. This was done because a lot of companies started installing add-ons in Firefox, and other browsers, without the users knowing it.
These may have been "security enhancement" add-ons part of antivirus suites, in the best case scenarios, or they might have been useless and spammy toolbars that also changed the default search engine, homepage and so on.
It was a good first step, but it wasn't enough. Mozilla is now stepping up enforcement of a rule that has always been there, add-ons must always ask permission before being installed.
This is the big reason why Mozilla was forced to scan and disable third-party add-ons in the first place. Some add-ons installed by third parties ask for permission in the software's installer, albeit most have the option "checked" by default. Some don't even do that.
And very few actually use the standard Firefox opt-in dialog despite Mozilla making it clear that no add-on should bypass it. Mozilla is now starting to enforce that rule and will go as far as remotely disabling add-ons that don't comply.
"Even if an add-on has its own installer, the Firefox add-on opt-in dialog is not optional and must be displayed every time a new add-on is installed from outside of Firefox. Mozilla will take appropriate measures to ensure this is happening, including remotely disabling violating add-ons. This policy applies to all add-ons except those distributed in an enterprise or controlled environment," Mozilla explained
That's a very good development that should, hopefully, mean that users have more choice in what their browsing experience is. It should also mean less people with browsers slowed down by add-ons or sleazy companies making money off of unwitting users.