Multiple cross-site scripting (XSS) vulnerabilities in Moodle through 2.3.11, 2.4.x before 2.4.11, 2.5.x before 2.5.7, 2.6.x before 2.6.4, and 2.7.x before 2.7.1 allow remote attackers to inject arbitrary web script or HTML via vectors that trigger an AJAX exception dialog.