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Vulnerability record · CVE-2026-84803 · published 2 September 2026

CVE-2026-84803: Cross-site scripting vulnerability

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.

8.6 CVSS 4.0 High EPSS 0.43% · top 65.5% CWE-79 · Cross-site scripting Deferred
8.6CVSS 4.0 base score
0.43%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
2 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-incomplete-asset-blocklist
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g

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Source: NIST National Vulnerability Database (record CVE-2026-84803), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.