Directory traversal vulnerability in (1) usercp_register.php and (2) usercp_avatar.php for phpBB 2.0.11, and possibly other versions, with gallery avatars enabled, allows remote attackers to delete (unlink) arbitrary files via "/../" sequences in the avatarselect parameter.
http://www.phpbb.com/support/documents.php?mode=changelog
http://www.idefense.com/application/poi/display?id=205&type=vulnerabilities