** DISPUTED **  postfix_groups.pl in Postfix 2.5.2 allows local users to overwrite arbitrary files via a symlink attack on the (1) /tmp/postfix_groups.stdout, (2) /tmp/postfix_groups.stderr, and (3) /tmp/postfix_groups.message temporary files.  NOTE: the vendor disputes this vulnerability, stating "This is not a real issue ... users would have to edit a script under /usr/lib to enable it."