Tested in FF57 on a few pages and it seems to work OK, but it doesn't work on the addons.mozilla.org itself (even after refreshing the page, quitting FF, etc.) I don't pretend to understand the bit about the CSP - is that the issue? Anyway, since the links on your extension's homepage are likely to be the first that someone who just installed the extension are going to try, you may want to issue a warning that the extension might not work on addons.mozilla.org

Due to your very nice icon this is my favorite addon for quickly copying a links target address; however, it doesnt seem to show up in the other addon Menu Wizard; is there anything you can do to fix that?

This is one of the handful of extensions that I can't do without, but why do you have to create a notification every time it is used? I use it many times a day and this is extremely annoying. At least give us a way to disable notifications if for some reason you want to spam users by default.