Symptoms
OA platform has been upgraded to version 7.0.
Strange users with login names like store[ID]apiuser[ID] (store28apiuser1000070) have been created with Store Full Access BA role and Staff member defaults OA role.
By their nature they are staff members' copies, inheriting complete contact details.
Cause
They were created automatically during the upgrade procedure.
Resolution
Please, refer to the Synchronizing Online Store documentation article for detailed explanation.