phpBB 2.0.17 and earlier, when the register_long_arrays directive is disabled, allows remote attackers to modify global variables and bypass security mechanisms because PHP does not define the associated HTTP_* variables.

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.

Multiple cross-site scripting (XSS) vulnerabilities in phpBB 2.0.14 and earlier allow remote attackers to inject arbitrary web script or HTML via the (1) u parameter to profile.php, (2) highlight parameter to viewtopic.php, or (3) forumname or forumdesc parameters to admin_forums.php.

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.