xlockmore and xlockf do not properly cleanse user-injected format strings, which allows local users to gain root privileges via the -d option.
archives.neohapsis.com/archives/bugtraq/2000-08/0212.html
archives.neohapsis.com/archives/bugtraq/2000-08/0294.html
archives.neohapsis.com/archives/freebsd/2000-08/0340.html
www.debian.org/security/2000/20000816
www.securityfocus.com/bid/1585
www.securityfocus.com/templates/archive.pike?list=1&msg=20000815231724.A14694%40subterrain.net