Firefox 1.0.3 and 1.0.4, and Netscape 8.0.2, allows remote attackers to execute arbitrary code by tricking the user into using the "Set As Wallpaper" (in Firefox) or "Set as Background" (in Netscape) context menu on an image URL that is really a javascript: URL with an eval statement, aka "Firewalling."
Exploitability
AV:NAC:HAu:NImpact
C:PI:PA:P5.1/AV:N/AC:H/Au:N/C:P/I:P/A:P