CVE-2026-87811 SiYuan before v3.8.2 Stored XSS via notebook template paths
Attackers can execute JavaScript in victims' browsers via malicious notebook template paths, enabling same-origin API requests and state manipulation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-87811?
CVE-2026-87811 is a high-severity cross-site scripting vulnerability in siyuan-note siyuan, published on 9 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-87811?
How do I fix CVE-2026-87811?
No fix has been published for CVE-2026-87811 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-87811 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87811 exists.
Sources
Also known as GHSA-qx37-mp6w-43mm, GHSA-v6wf-r2gr-rrgf.