CVE-2026-73630: SiYuan before v3.7.4 Information Disclosure via authFilePublishAccess

SiYuan before v3.7.4 contains an information disclosure vulnerability in the /api/filetree/authFilePublishAccess endpoint, which is registered with CheckAuth only and is reachable anonymously. The endpoint never sets a failure code, so its outcome is signalled entirely by the response message and by the presence of a Set-Cookie header, and these signals differ across access tiers. By submitting requests with an empty password for a candidate document identifier, an anonymous attacker can distinguish whether a document is public/nonexistent, password-protected, or exists at the hidden or forbidden tier, thereby confirming the existence of documents they are not permitted to access. Because hidden and forbidden entries store an empty password, such requests also cause the server to issue a publish-auth cookie for forbidden documents.