CVE-2026-84803

Critical

Description

SiYuan before v3.8.2 contains a stored cross-site scripting vulnerability in asset serving due to an incomplete extension blocklist that misses script-capable file types. Attackers can upload files with extensions like .xht, .ehtml, .xsl, .xbl, or .rdf that resolve to executable media types and execute JavaScript to steal API tokens and compromise workspaces.

SeverityCritical

CVSS9.0

Exploit probability—

ProductSiyuan

PublishedSep 2, 2026

First seenSep 2, 2026

Weakness typeCWE-79Cross-site scripting (XSS)

How to fix

Update

siyuan-note siyuan3.8.2 or later

Vendor advisories

github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g

Affected products

Product	Affected versions	Fixed in
siyuan-note siyuan	v < 3.8.2	3.8.2

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