The print_test_result function in admin/upgrade_unattended.php in MantisBT 1.1.0a3 through 1.2.x before 1.2.18 allows remote attackers to obtain database credentials via a URL in the hostname parameter and reading the parameters in the response sent to the URL.
https://github.com/mantisbt/mantisbt/commit/0826cef8
https://exchange.xforce.ibmcloud.com/vulnerabilities/99031
http://www.securityfocus.com/bid/71359