Cluster Security reboot alert.
By default, Cluster Security is disabled. Any changes made to this feature, such as disable/enable, IAP cluster needs to be rebooted for the changes to take effect. As we can see in the below UI monitoring tab(AP Alerts), reboot alert is shown as changes were made to Cluster Security feature. It's mandatory to reboot the entire cluster(all the APs in the cluster) and not just the Virtual Controller.
WLAN admin needs to schedule a downtime, if he wants to make any changes to this feature.