SiYuan versions before 3.7.3 expose the getHeadingDeleteTransaction, getHeadingLevelTransaction, and getHeadingInsertTransaction endpoints to return rendered block DOM without performing publish‑access checks. This flaw allows anyone with an anonymous or RoleReader token to supply a heading block ID and retrieve the fully rendered content of documents that should be publish‑disabled. The vulnerability constitutes a critical information disclosure, enabling attackers to read confidential material that was intended to remain restricted.

All releases of the Siyuan‑note Siyuan product with a version number lower than 3.7.3 are affected. Administrators should confirm that their deployment is at least v3.7.3, as earlier releases contain the flaw.

The CVSS score of 9.2 classifies the issue as critical, and the absence of an authentication requirement makes exploitation trivial for anyone who can reach the API. Although the EPSS score is not published, the high severity and the presence of a security advisory indicate a substantial risk. The vulnerability is not listed in the CISA KEV catalog, so no publicly known exploits exist yet, but the exposed endpoints provide a broad attack surface across any network that can connect to the Siyuan instance.