SiYuan before v3.8.5 contains a missing authorization vulnerability in the getRefCreateSavePath, getShorthandSavePath, and getDocCreateSavePath endpoints that allows read-only publish visitors to learn unpublished notebook box IDs. Attackers with read-only or anonymous publish access can POST any open notebook ID to receive the global save-box ID and save-path template, revealing a hidden notebook's existence and creation time.