xscreensaver 5.03 and earlier, when running without xscreensaver-gl-extras (GL extras) installed, crashes when /usr/bin/xscreensaver-gl-helper does not exist and a user attempts to unlock the screen, which allows attackers with physical access to gain access to the locked session.
https://www.redhat.com/archives/fedora-package-announce/2007-October/msg00336.html
https://bugzilla.redhat.com/show_bug.cgi?id=336331