The activation resend function in the Profiles module in XOOPS before 2.4.1 sends activation codes in response to arbitrary activation requests, which allows remote attackers to bypass administrative approval via a request involving activate.php.

Multiple unspecified vulnerabilities in XOOPS before 2.4.0 Final have unknown impact and attack vectors.

mainfile.php in XOOPS 2.0.13.2 and earlier, when register_globals is enabled, allows remote attackers to overwrite variables such as $xoopsOption['nocommon'] and conduct directory traversal attacks or include PHP files via (1) xoopsConfig[language] to misc.php or (2) xoopsConfig[theme_set] to index.php, as demonstrated by injecting PHP sequences into a log file.

SQL injection vulnerability in the loginUser function in the XMLRPC server in XOOPS 2.0.11 and earlier allows remote attackers to execute arbitrary SQL commands and bypass authentication via crafted values in an XML file, as demonstrated using the blogger.getPost method.

Multiple cross-site scripting (XSS) vulnerabilities in XOOPS 2.0.11 and earlier allow remote attackers to inject arbitrary web script or HTML via the (1) order parameter to edit.php or (2) cid parameter to comment_edit.php.

The custom avatar uploading feature (uploader.php) for XOOPS 2.0.9.2 and earlier allows remote attackers to upload arbitrary PHP scripts, whose file extensions are not filtered.