Multiple cross-site scripting (XSS) vulnerabilities in tmpl/layout_editevent.php in the Multi Calendar (com_multicalendar) component 4.0.2, and possibly 4.8.5 and earlier, for Joomla! allow remote attackers to inject arbitrary web script or HTML via the (1) calid or (2) paletteDefault parameter in an editevent action to index.php.