CVE 2005-0673

Cross-site scripting (XSS) vulnerability in usercp_register.php for phpBB 2.0.13 allows remote attackers to inject arbitrary web script or HTML by setting the (1) allowhtml, (2) allowbbcode, or (3) allowsmilies parameters to inject HTML into signatures for personal messages, possibly when they are processed by privmsg.php or viewtopic.php.

See the CVE page on Mitre.org for more details.