Note attachments are private by default
New documents uploaded as attachments through Notes are now private by default and are stored in the Notes attachments folder under Documents. When sharing a document you can choose a Public link, Private link, OTP-protected link, or Password-protected link.
Existing documents uploaded through Notes before this release stay public and unchanged; you can still generate and share a Private link for an existing document when you need more access control.
See Share a note attachment with a private link for the details.