There is nothing to see at this address on its own. Each campaign has its own link, and every link carries a signature — that is what stops anyone who finds this address from browsing your drafts.
Open it from the approval email instead. Every approval email has a See it full size button, and that button is the link.
A link looks like /c/53?t=…. Without the part after
t=, or with it altered, this page shows nothing.