MDL-14461:

The user must be (effectively) be logged in to use this function.
Adding the logged in check means they will be asked if they are not (like
everywhere else)

auth/mnet/jump.php

@@ -14,6 +14,8 @@
 
 require_once dirname(dirname(dirname(__FILE__))) . '/config.php';
 
+require_login();
+
 if (!is_enabled_auth('mnet')) {
     error('mnet is disabled');
 }