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!
please confirm that the plugin that you are trying to remove is located in .mozilla/ firefox/ YOURPROFILE. default/ extensions
/home/youruser/
If the extension that you want to remove is firefox/ extensions you can't
located /usr/lib/
remove it from firefox as a normal user.
Thank you for your report!