CVE-2026-87809 [MEDIUM] – Siyuan before v3.8.2 fails to apply publish-access filtering to embedded blocks before ren

Siyuan before v3.8.2 fails to apply publish-access filtering to embedded blocks before rendering in the /api/export/preview and /api/lute/copyStdMarkdown endpoints. Attackers with reader access can retrieve the full rendered content of private, hidden, or publish-disabled blocks by accessing public documents containing embed queries that select those blocks.