So, I was checking to see if my antivirus was actually doing its job... Noticed it was scanning a bunch of Firefox cache and was giving a re-assuring green check mark. I decided to do some binary analysis on one of the scanned files. It looked like some binary or encrypted content with a text header and footer. Popped open a hex editor, googled wtf JFIF stood for. Saw a pretty logo for JPEG so I changed the file extension of this "file" file to ".jpeg" and voila, a super compressed cache image. Green checkmark was right!