# 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.

- **Severity:** High 8.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N`)
- **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 available:** No
- **Published:** 6 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** GHSA-qwcw-r653-j8c6

## 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 (Improper Neutralization of Input During Web Page Generation)

## 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.

## Is CVE-2026-105798 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-105798 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-105798 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-105798 exists.

Affected product: microsoft simplechat. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-105798/ (Markdown: https://insights.sbomify.com/CVE-2026-105798/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-105798
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-105798
- OSV: https://osv.dev/vulnerability/CVE-2026-105798

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-105798/
Summaries are generated and may contain mistakes; the official description above is the record.