When filling out a form to purchase something, the type ahead filled out the rest of my credit card number. I tracked it down to the formhistory.sqlite file. The number was in human readable form and labeled as a card number. The authorization code was also in the file. I also found the information in a formhistory.dat file but not quite as easy to read. Both files had permission to be read by everyone. I did not find a way to disable the formhistory feature. I have deleted the files, touched the files (UNIX command which creates a zero length file), and changed the permissions so that I can not write to the files. I do not know how FF will react to this.