Cross-site scripting (XSS) vulnerability in the user_get_user_details function in user/lib.php in Moodle through 2.6.11, 2.7.x before 2.7.9, 2.8.x before 2.8.7, and 2.9.x before 2.9.1 allows remote attackers to inject arbitrary web script or HTML by leveraging absence of an external_format_text call in a web service.

Open redirect vulnerability in the clean_param function in lib/moodlelib.php in Moodle through 2.6.11, 2.7.x before 2.7.9, 2.8.x before 2.8.7, and 2.9.x before 2.9.1 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via vectors involving an HTTP Referer header that has a substring match with a local URL.

message/externallib.php in Moodle through 2.5.9, 2.6.x before 2.6.7, 2.7.x before 2.7.4, and 2.8.x before 2.8.2 allows remote authenticated users to bypass a messaging-disabled setting via a web-services request, as demonstrated by a people-search request.

tag/user.php in Moodle through 2.5.9, 2.6.x before 2.6.9, 2.7.x before 2.7.6, and 2.8.x before 2.8.4 does not consider the moodle/tag:flag capability before proceeding with a flaginappropriate action, which allows remote authenticated users to bypass intended access restrictions via the "Flag as inappropriate" feature.

lib/navigationlib.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 allows remote authenticated users to obtain sensitive course-structure information by leveraging access to a student account with a suspended enrolment.

calendar/externallib.php in Moodle through 2.5.9, 2.6.x before 2.6.7, 2.7.x before 2.7.4, and 2.8.x before 2.8.2 allows remote authenticated users to obtain sensitive calendar-event information via a web-services request.

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.

mod/lti/ajax.php in Moodle through 2.5.9, 2.6.x before 2.6.7, 2.7.x before 2.7.4, and 2.8.x before 2.8.2 does not consider the moodle/course:manageactivities and mod/lti:addinstance capabilities before proceeding with registered-tool list searches, which allows remote authenticated users to obtain sensitive information via requests to the LTI Ajax service.

login/confirm.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 allows remote authenticated users to bypass intended login restrictions by leveraging access to an unconfirmed suspended account.

message/index.php in Moodle through 2.5.9, 2.6.x before 2.6.9, 2.7.x before 2.7.6, and 2.8.x before 2.8.4 does not consider the moodle/site:readallmessages capability before accessing arbitrary conversations, which allows remote authenticated users to obtain sensitive personal-contact and unread-message-count information via a modified URL.