http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/etc/group?rev=1.99&content-type=text/x-cvsweb-markup

_shutdown group now allows to use /sbin/shutdown
Index: xfce4-session/xfsm-shutdown-fallback.c
--- xfce4-session/xfsm-shutdown-fallback.c.orig
+++ xfce4-session/xfsm-shutdown-fallback.c
@@ -241,7 +241,7 @@ xfsm_shutdown_fallback_user_is_operator (void)
       struct group *gr;
 
       gr = getgrgid (groups[i]);
-      if (gr != NULL && strncmp(gr->gr_name, "operator", 8) == 0)
+      if (gr != NULL && strncmp(gr->gr_name, "_shutdown", 9) == 0)
         {
           is_operator = TRUE;
           break;