The KDE kscd program does not drop privileges when executing a program specified in a user's SHELL environmental variable, which allows the user to gain privileges by specifying an alternate program to execute.
http://www.securityfocus.com/bid/1206
http://www.novell.com/linux/security/advisories/suse_security_announce_50.html
http://archives.neohapsis.com/archives/bugtraq/2000-05/0172.html