Cross-site scripting (XSS) vulnerability in the private message box implementation (privmsg.php) in phpBB 2.0.x allows remote authenticated users to inject arbitrary web script or HTML via the "Message body" field in a message to a non-existent user.
https://exchange.xforce.ibmcloud.com/vulnerabilities/30776
http://www.securityfocus.com/bid/22001
http://www.securityfocus.com/bid/21806
http://www.securityfocus.com/archive/1/456784/100/100/threaded
http://www.securityfocus.com/archive/1/456728/100/100/threaded
http://www.securityfocus.com/archive/1/456579/100/0/threaded
http://www.securityfocus.com/archive/1/453774/100/0/threaded
http://www.phpbb.com/phpBB/viewtopic.php?f=14&t=489624