What is .FBU file extension?
Collection of Firefox extensions and other data backed up with FEBE, a Firefox backup program; may contain extensions, themes, bookmarks, preferences, and user cookies; can store extensions as a single .XPI file, which can be used to sync Firefox settings across multiple computers.
FEBE stands for "Firefox Environment Backup Extension."
You can see a list of software programs here on www.easyfileopener.org that can open this file type so that you don’t need to search for it on the web. You can then open your file with this extension using a software listed below.