SQL injection vulnerability in usercp_register.php in phpBB 2.0.17 allows remote attackers to execute arbitrary SQL commands via the signature_bbcode_uid parameter, which is not properly initialized.

phpBB 2.0.17 and earlier allows remote attackers to bypass protection mechanisms that deregister global variables by setting both a GET/POST/COOKIE (GPC) variable and a GLOBALS[] variable with the same name, which causes phpBB to unset the GLOBALS[] variable but not the GPC variable.

Multiple cross-site scripting (XSS) vulnerabilities in phpBB 2.0.17 and earlier allow remote attackers to inject arbitrary web script or HTML via the (1) error_msg parameter to usercp_register.php, (2) forward_page parameter to login.php, and (3) list_cat parameter to search.php, which are not initialized as variables.

phpBB 2.0.17 and earlier, when register_globals is enabled and the session_start function has not been called to handle a session, allows remote attackers to bypass security checks by setting the $_SESSION and $HTTP_SESSION_VARS variables to strings instead of arrays, which causes an array_merge function call to fail.

usercp_register.php in phpBB 2.0.17 allows remote attackers to modify regular expressions and execute PHP code via the signature_bbcode_uid parameter, as demonstrated by injecting an "e" modifier into a preg_replace statement.

The bbencode_second_pass and make_clickable functions in bbcode.php for phpBB before 2.0.15, as used in viewtopic.php, privmsg.php, and other scripts, allow remote attackers to execute arbitrary script via a BBcode tag with a (1) javascript:, (2) applet:, (3) about:, (4) activex:, (5) chrome:, or (6) script: URI scheme, as demonstrated using the URL tag.

sessions.php in phpBB 2.0.12 and earlier allows remote attackers to gain administrator privileges via the autologinid value in a cookie.

phpBB 2.0.13 and earlier allows remote attackers to obtain sensitive information via a direct request to oracle.php, which reveals the path in a PHP error message.

Meilad File upload script (up.php) mod for phpBB 2.0.x does not properly limit the types of files that can be uploaded, which allows remote authenticated users to execute arbitrary commands by uploading PHP files, then directly requesting them from the uploads directory.

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.