Hey,this one is pretty old,but i havent seen THIS version of it on the forums.
As you know it's able to see YOUR own passwords by checking into the "Tools" tab in Firefox,but it's also possible to see other ones.
Start your DC++ or any other p2p downloader program or w/e
Search for signons.txt/signons2.txt and KEY3.DB (Both files gotta be from the same person,that's why DC++ is prefered)
Then put em in the "Firefox\Profiles\Profile Folder" Save your own ones if you wanna keep having them,or just overwrite em.
Start Firefox and go into Tools -->Settings --> Security --> Saved Password's
The larger the file's your downloading are , the more password's they contain,so dont download if they are like 0kb,as the person havent saved any password's then.
I've gotten PayPal accounts,WoW accounts by using this.
Thanks
EDIT: If i remember right,one of the files named signon ,well it's signon.txt for the older firefox version and signon2.txt for the newer,there's no different exept the name.
EDIT2: Pictures at page 2.