CVE-2026-87811: SiYuan before v3.8.2 Stored XSS via notebook template paths

Severity: high (CVSS 7.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-09 · updated 2026-09-09
Weakness: CWE-79

Description

SiYuan before v3.8.2 inserts persisted notebook template paths into HTML input value attributes without proper attribute encoding. Attackers can craft malicious template paths that break out of the attribute context and execute JavaScript when a victim opens notebook configuration, enabling same-origin API requests and application state manipulation.

Affected products

siyuan-note siyuan: before 3.8.2 — fixed in 3.8.2

How to fix

Upgrade to a fixed version: siyuan-note siyuan 3.8.2. Check the vendor advisory for mitigations.

References

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

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