I use Domain Access with several ALIAS Domains. But webform private upload only secures the files for the STANDARD domain not for the ALIAS domains and NOT for the direct access via IP address

for example:

www.example.com/sites/default/files/webform/private/testfile.jpg -> access denied
example.com/sites/default/files/webform/private/testfile.jpg -> access NOT denied
[IP address]/sites/default/files/webform/private/testfile.jpg -> access NOT denied

can anyone you help me please?