From v4.2.12 you can enable system boot hardening from the Management UI.
With boot hardening enabled the taskbar on the desktop will be not be loaded, thereby disallowing any PC functionality to a user until the Kiosk starts.
If you get an error "failed to enable", and you see in the log the error(Screenshot), the problem is with the permissions of the local user.
You need to change the permissions from MMC - "Component Services" (search the APPID from Event viewer log). OR uninstall the Kiosk that installed with the current user, create a new local user, install the Kiosk again, and try to enable the System boot hardening.