mod/quiz/db/access.php in Moodle through 2.5.9 2.6.x before 2.6.11 2.7.x before 2.7.8 and 2.8.x before 2.8.6 does not set the RISK_XSS bit for graders which allows remote authenticated users to conduct cross-site scripting (XSS) attacks via crafted gradebook feedback during manual quiz grading.