After installing Firefox plugins you progressively loose control of menus, especially the right click menu where I found a lots of features that I never use from there. So why scrolling every time the menu, and there is an extension like Menu Editor. The extension simply rearrange or remove menuitems from the main context menu and main menubar. You will certainly figure out many useless menu items that you used to access from the top menu or keyboard shortcuts. Now you should be able to install anything safely, and keeping 100% control on the menus in case it start scrolling.
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