If this occurs in your OC make sure you advise your insurance company, in writing. Then if there is an increase in premiums the owner is liable for them. Even if there is no additional cost, the insurance company does require that they be informed if there may be increased risk to the premises they’re providing coverage.
Do this in writing immediately, and make sure your OC manager knows that this is very serious and must be actioned immediately.
Maybe the legal person who is au fait with Victorian OC law could advise if the cost of any additional security that is required could be paid for by the owner?