Extensions for Firefox installed via the Install/Remove Extensions app are not removable.

You can remove extensions installed by the root if you install the extension via
Gnome Add/Remove as root you cant remove it from firefox as a normal user.

Thanks for your report!

This actually occurred when launched without admin permissions (no sudo, or su) nothing was installed as root, just as a normal user.

Here's the steps I took to find this bug, launch Firefox, Tools, Addons, Get Ubuntu Addons, Select Adblock from the list. Install it. Now try and remove it through the Add/Remove Extensions window even after closing Firefox and the Add/Remove Extensions window and restarting Firefox.

This was done on the initial account created during Ubuntu setup, Firefox was launched via the Gnome menu, no commands or elevations (su, sudo, gksudo) were used. After installing the addon as a normal user I'd expect to be able to remove it as a normal user through Firefox's own addon controls instead of requiring an external uninstaller to be launched (in this case the Add/Remove... link in the Gnome Menu).

please confirm that the plugin that you are trying to remove is located in
/home/youruser/.mozilla/firefox/YOURPROFILE.default/extensions

If the extension that you want to remove is
located /usr/lib/firefox/extensions you can't
remove it from firefox as a normal user.

Thank you for your report!

Mario I understand that, but without elevating the installer I can't install to /usr/lib anyway so it's obvious the addon is being installed to my profile.default/extensions subdirectory.

The bug is simply that the Ubuntu Supported addons can not be removed through the normal means, which is contrary to normal Firefox operation on other platforms, when bringing new users to Ubuntu it's nice to be able to tell them that everything is the same in Firefox after wrestling them away from Internet Explorer. There should be a single install/remove method in Firefox, which Mozilla have provided but it was disabled in the supported XPI's.