mod/lesson/pagetypes/matching.php in Moodle through 2.2.11, 2.3.x before 2.3.8, 2.4.x before 2.4.5, and 2.5.x before 2.5.1 allows remote authenticated users to obtain sensitive answer information by reading the HTML source code of a document.
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.