Earlier quoted context omitted.
Why is it a GDPR breach when a Dropbox screen clearly explains to the user clicking the link that other users will see your details if you proceed? (Just curious, it may well be an issue, I just don’t know how).
If I understand correctly this warning/explanation only appears for the user sharing the document, not for anyone else who opened it(and whose information is still embedded).
That’s not correct. Unless there’s been a temporary regression then the warning explicitly happens for the person opening the document (the person you have shared it with)