Firefox 42 will not allow unsigned extensions

How does this policy interact with greasemonkey, an extension that allows running random JavaScript on sites with access to the extension API. You could write your malware as a greasemonkey extension, convince a user to install a signed greasemonkey release, and then convince them to install your malicious extension.

Great point. Does anyone know what--if any--limits Grease Monkey puts in place to prevent users from bring exploited?