CVE-2026-105798 SimpleChat: Stored XSS via group document filename in inline onclick handler
An authenticated user can inject scripts via document filenames, executing code in other users' sessions to access data or take over accounts.
- 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-2026-105798?
CVE-2026-105798 is a high-severity cross-site scripting vulnerability in microsoft simplechat, published on 6 Oct 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
SimpleChat is a secure AI conversation application with personal and group workspaces for document-grounded interactions. Prior to 0.261.029, POST /api/group_documents/upload stores an attacker-controlled group document filename that group_workspaces.html later interpolates into inline Share event handlers. The escapeGroupHtml function leaves apostrophes unchanged, while escapeHtml produces an HTML entity that the browser decodes before JavaScript evaluation, so either path permits the filename to terminate the handler string. An authenticated group Owner, Admin, or DocumentManager can persist script that executes in the SimpleChat origin when another group member clicks Share, allowing access to victim-visible data and actions with the victim session. This issue is fixed in version 0.261.029.
Weakness: CWE-79
Which versions are affected by CVE-2026-105798?
How do I fix CVE-2026-105798?
No fix has been published for CVE-2026-105798 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-2026-105798 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-105798 exists.
Sources
Also known as GHSA-qwcw-r653-j8c6.