Multiple cross-site scripting (XSS) vulnerabilities in Dokeos 1.8.4 allow remote attackers to inject arbitrary web script or HTML via the (1) username parameter to inscription.php, (2) courseCode parameter to main/calendar/myagenda.php, (3) category parameter to main/admin/course_category.php, (4) message parameter to main/admin/session_list.php in a show_message action, and (5) an avatar image to main/auth/profile.php.