The remote web server is hosting a web application that is vulnerable to a remote header injection attack vector.
The remote web server hosts Moodle, an open-source course management system. Versions of Moodle 2.7.x prior to 2.7.15 are affected by a flaw that may allow an authenticated remote attacker to inject email addresses into the intended recipients of an email by changing their username to include another user's email address. This may result in other users potentially being saturated with emails. (CVE-2016-5013)
Upgrade to Moodle version 2.7.15 or later.