If the hack was conducted through the use of account hijacking then why didn't anybody at Citrix notice. Unless once the hackers got in they migrated within the

If the hack was conducted through the use of account hijacking then why didn't anybody at Citrix notice. Unless once the hackers got in they migrated within the network using as yet unknown vulnerabilities. Makes one wonder of there are backdoors in all networking equipment. So as the various state security entities can keep an eye on us.