FurAffinity Notifier+ by Kenji Kuroneki

Displays the number of FurAffinity messages the user has. Originally posted by David Maher on Chrome Web Store and modified and improved to Firefox Quantum. Now has options to display/hide favorites, watchers, comments, submissions and notes.

THIS EXTENSION IS DISCONTINUED, PLEASE USE MY NEW EXTENSION FABUI BELOW:
https://addons.mozilla.org/en-US/firefox/addon/fabui-fa/