Keymaster_XH facilitates locking the back-end of a CMSimple_XH website, if an admin is already logged in. This is necessary in case there is more than one admin who has access to the back-end, as the back-end of CMSimple_XH does not take any precautions against concurrent editing.

If an admin is already logged in to the site, other admins are informed that they cannot edit the site, and logging out is suggested to them. After a configurable period of inactivity, another admin can take over the administration session, in which case the previous admin is denied further editing of the site for the time being.