---
title: "CVE-2026-87811: SiYuan - Stored XSS"
description: "SiYuan < 3.8.2 contains a stored XSS caused by improper attribute encoding of persisted notebook template paths in HTML input value attributes, letting attackers execute JavaScript when victims open notebook configuration, exploit requires crafted malicious template paths."
url: https://panop.io/threat-heartbeat/CVE-2026-87811/
---

# CVE-2026-87811 SiYuan - Stored XSS

SiYuan < 3.8.2 contains a stored XSS caused by improper attribute encoding of persisted notebook template paths in HTML input value attributes, letting attackers execute JavaScript when victims open notebook configuration, exploit requires crafted malicious template paths.

CVSS base score 7.3 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.37% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-87811)

## Details

Type

Stored XSS

Impact

Stored XSS

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

Published

9 September 2026

Updated

15 October 2026

Weakness

[CWE-79](https://cwe.mitre.org/data/definitions/79.html)

## Vendor fix

Update to version 3.8.2 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-87811](https://nvd.nist.gov/vuln/detail/CVE-2026-87811)
- [https://github.com/siyuan-note/siyuan/security/advisories/GHSA-v6wf-r2gr-rrgf](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-v6wf-r2gr-rrgf)
- [https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-notebook-template-paths](https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-notebook-template-paths)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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