"loolforkit" is a privileged program that is supposed to be run by a special, non-privileged "lool" user. Before doing anything else "loolforkit" checks, if it was invoked by the "lool" user, and refuses to run with privileges, if it's not the case. In the vulnerable version of "loolforkit" this check was wrong, so a normal user could start "loolforkit" and eventually get local root privileges.