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High 8.7Published Oct 6, 2026

CVE-2026-105798SimpleChat: Stored XSS via group document filename in inline onclick handler

Updated under an hour ago ()

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It affects microsoft simplechat. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.46%, higher than 39% of scored CVEs.

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.

CVSS
8.7 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
Weakness (CWE)
CWE-79
Known exploited
Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days)
0.46% (percentile 39)
Assigned by
GitHub_M
NVD analysis
Deferred
Record last updated
Oct 6, 2026
First seen by InfoSec Signals
Oct 9, 2026

Affected products

Affected products
microsoft simplechat
microsoft:simplechat (from the name)
before 0.261.029
CNA record

References

  • x-refsource-confirm
  • x-refsource-misc

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.

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