This issue is triggered when you have a file uploader on your Bubble page, and the checkbox "Make this file private" is not checked.
When this checkbox is left unchecked, it means that all the files uploaded through this file uploader will be public.
If you're uploading invoices, ID documents, or estimates, you probably don't want them to be accessible to everyone.
Solution
In order to fix this issue, the only thing you have to do is to check the "Make this file private" checkbox and link it to the according data type.
Like this: