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 cross-site scripting (XSS) vulnerabilities in XOOPS 2.0.12 JP and earlier, XOOPS 2.0.13.1 and earlier, and 2.2.x up to 2.2.3 RC1 allow remote attackers to inject arbitrary web script or HTML via (1) modules that use "XOOPS Code" and (2) newbb in the forum module.

mainfile.php in XOOPS 2.0.13.2 and earlier, when registerglobals 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[themeset] to index.php, as demonstrated by injecting PHP sequences into a log file.