SiYuan versions before v3.7.3 contain a vulnerability where publish-access filters are not applied to the getBacklinkDoc and getBackmentionDoc content endpoints. While backlink list endpoints correctly filter publish-forbidden documents, the content endpoints are only gated by CheckAuth, leaving them accessible to publish-mode readers. An anonymous reader, when publish Basic Auth is disabled, can directly call these endpoints using a publish-forbidden document's ID to retrieve rendered DOM content. This also enables a reference-existence oracle attack, allowing the attacker to determine whether a document references a specific block. The flaw represents an improper access control issue in SiYuan's publish mode functionality. The vulnerability has been assigned CVE-2026-68586 and is patched in v3.7.3.