I am not familiar with how CS is or can be administered.

As a customer you should not have to assume the software your supplier vends is faulty to the extent of this incident.

It's reasonable for a customer to assume the software is tested according to industry best practices.

CS acted grossly negligent here, and they deserve the majority of the blame.

I agree that some blame also resides with customers, there must be disaster recovery procedures in place to allow them to function with minimal downtime in the case of emergency services.