I Just updated from 17.xx to 18.0.2 yesterday. Today when I logged onto my computer, Firefox icons were gone from my desktop and when I find and run Firefox directly from the mozilla firefox directory, my bookmarks , homepage, and other settings are all gone! WTF?!?
Additional info, I'm using an SSD as my boot/program drive and had altered F to use my data drive (D) for temporary cache files. I'm guessing it has something to do with this, but seriously... no reason it should.