CVE-2026-87807 is an authenticated SQL injection vulnerability affecting siyuan-note's siyuan product versions prior to 3.8.2. The vulnerability exists in the fullTextSearchBlock endpoint, specifically in the method=1 query parameter, which does not properly neutralize special elements used in SQL commands. Exploiting this flaw, attackers can inject UNION SELECT statements to retrieve the entire blocks table, thereby bypassing publish-access controls and exposing all document content and sensitive attributes stored in the database.

Successful exploitation results in unauthorized disclosure of all document content and sensitive attributes stored in the blocks table. This bypasses intended access controls, potentially exposing sensitive user data to authenticated attackers.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to the vulnerable endpoint to trusted users only and monitor for suspicious activity related to the fullTextSearchBlock endpoint.