Directory traversal vulnerability in newpost.php in Ultimate PHP Board (UPB) 1.9.6 and earlier allows remote attackers to overwrite arbitrary files via a .. (dot dot) sequence and trailing null (%00) byte in the id parameter, as demonstrated by injecting a Perl CGI script using "[NR]" sequences in the message parameter, then calling close.php with modified id and t_id parameters to chmod the script.  NOTE: this issue might be resultant from dynamic variable evaluation.