The LTI module in Moodle through 2.4.11, 2.5.x before 2.5.9, 2.6.x before 2.6.6, and 2.7.x before 2.7.3 does not properly restrict the parameters used in a return URL, which allows remote attackers to trigger the generation of arbitrary messages via a modified URL, related to mod/lti/locallib.php and mod/lti/return.php.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.