A zero-day vulnerability is a known security flaw that is known to the software vendor but doesn’t have a patch in place to fix the flaw. As a result, it has the potential to be exploited by bad actors.

Since an official fix is not yet in place, the best thing a site owner can do is have frequent off-site backups so that if a hack does occur, recovery can be quick.

I’d also review the type of information stored on the site and place limits on the type of info and how long it stays there.