misc.c in splitvt 1.6.6 and earlier does not drop group privileges before executing xprop, which allows local users to gain privileges.
http://www.securityfocus.com/bid/27936
http://www.debian.org/security/2008/dsa-1500
http://security.gentoo.org/glsa/glsa-200803-05.xml
http://secunia.com/advisories/29190