SQL injection vulnerability in privmsg.php in phpBB 2.0.3 and earlier allows remote attackers to execute arbitrary SQL commands via the mark[] parameter.
http://www.securityfocus.com/archive/1/307212/30/26300/threaded
http://secunia.com/advisories/7887/
http://archives.neohapsis.com/archives/bugtraq/2003-01/0125.html