Supplier can view the saved PO in SUS

Hi Experts,

We are in SRM701 and ECC6 EHP4,

Scenario: Create PO in ECC,

When PO is created and saved in ECC, the supplier is able to view the saved PO in SUS . under order collaboration tab -- > create document -> external confirmation.

Why is the supplier able to view the saved PO is SUS ? please advise.

Regards

Kumar