In reply to Davide.

Those are just numbers. Many wordpress security issues are related to user privilege escalation and if that site did not have open user registration it would not have been effected.

Just because there is some security issue do not mean that it can be abused. A very basic security measure in this kind of setup will be to limit access to the admin to the IP addresses of the office and then 90% of security issues can not be exploited in practice.