The remote web server contains a PHP script that allows arbitrary command execution.
The version of MyBB installed on the remote host fails to sanitize input to the 'sortby' parameter of the 'forumdisplay.php' script before using it in an 'eval()' statement to evaluate PHP code. An unauthenticated attacker can leverage this issue to execute arbitrary code on the remote host subject to the privileges of the web server user ID. In addition, this version of MyBB is vulnerable to several SQL injection attacks that, if exploited, would give the attacker the ability to execute arbitrary SQL commands on the database server utilized by MyBB.
Upgrade to version 1.2.11 or higher.