Mozilla Foundation Security Advisory 2013-74

Firefox full and stub installer DLL hijacking

August 6, 2013
Robert Kugler, Brian Bondy, Robert Strong
Firefox, SeaMonkey
Fixed in
  • Firefox 23
  • SeaMonkey 2.20


Security researcher Robert Kugler reported in 2012 that when a specifically named DLL file on a Windows computer is placed in the default downloads directory with the Firefox installer, the Firefox installer will load this DLL file when it is launched. Mozilla developers Brian Bondy and Robert Strong then discovered that the stub installer was vulnerable to this same issue with a number of DLL files and there were additionally vulnerable named DLL files with the full installer. In circumstances where an installer is run by an administrator privileged account, this allows for a downloaded DLL file to be run with those administrator privileges.