CVE-2026-84803 SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist
Attackers can upload malicious files to execute JavaScript and steal API tokens in SiYuan note-taking application.
- 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-2026-84803?
CVE-2026-84803 is a high-severity cross-site scripting vulnerability in siyuan-note siyuan, published on 2 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 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-84803?
How do I fix CVE-2026-84803?
No fix has been published for CVE-2026-84803 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-2026-84803 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84803 exists.
Sources
Also known as GHSA-73j8-px8h-3w2h, GHSA-7h8j-qw37-w46g.