A flaw was found in moodle versions 3.5 to 3.5.2, 3.4 to 3.4.5, 3.3 to 3.3.8, 3.1 to 3.1.14 and earlier. The login form is not protected by a token to prevent login cross-site request forgery. Fixed versions include 3.6, 3.5.3, 3.4.6, 3.3.9 and 3.1.15.
https://moodle.org/mod/forum/discuss.php?d=378731
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16854
http://www.securitytracker.com/id/1042154
http://www.securityfocus.com/bid/106017
http://git.moodle.org/gw?p=moodle.git&a=search&h=HEAD&st=commit&s=MDL-63183