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.