lib/setuplib.php in Moodle through 2.1.10, 2.2.x before 2.2.8, 2.3.x before 2.3.5, and 2.4.x before 2.4.2 allows remote attackers to obtain sensitive information via an invalid request, which reveals the absolute path in an exception message.
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.