[vetinari]

That doesn't help, when you really needed an unsigned extension, or at least signed with your own key (and enroll your own key to firefox installation).

For example, FreeIPA used to have an extension, that configured Firefox to your own domain (enrolled an root signing certificate, configured trusted domains for GSSAPI, etc. - all the dangerous things). But because the extension was customized for your own domain, obviously, it could not be signed.

So, it was killed instead. Nowadays, you get a list of steps, you have to do by hand. On every desktop.