In Moodle 2.x and 3.x, a CSRF attack is possible that allows attackers to change the "number of courses displayed in the course overview block" configuration setting.
Cross-site scripting (XSS) vulnerabilities in Moodle CMS on or before 3.1.2 allow remote attackers to inject arbitrary web script or HTML via the s_additionalhtmlhead, s_additionalhtmltopofbody, and s_additionalhtmlfooter parameters.