Mozilla Firefox before 2.0.0.5, when run on Windows, allows remote attackers to bypass file type checks and possibly execute programs via a (1) file:/// or (2) resource: URI with a dangerous extension, followed by a NULL byte (%00) and a safer extension, which causes Firefox to treat the requested file differently than Windows would.
Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.