Incorrect Access Control in Nagios Fusion 4.1.8 and earlier allows low-privileged authenticated users to extract passwords used to manage fused servers via the test_server command in ajaxhelper.php.
https://www.nagios.com/downloads/nagios-xi/change-log/
https://skylightcyber.com/2021/05/20/13-nagios-vulnerabilities-7-will-shock-you/