Today we released Nagios XI 5.6.3 which includes a number of updates related to security and permissions. The PHPMailer library has been updated to 5.2.27 to address a number of notable security improvements. We have also corrected a function inside the PHPMailer where AutoTLS was enabled by default. Other improvements include updates to the Schedule Downtime feature, SNMP Traps, and resolved discrepancies with PHP upgrades on certain RHEL systems.
For a full list of improvements, check out our Nagios XI Change Log