MSRC-CVE-2026-88209 — Microsoft Office SharePoint Spoofing Vulnerability

Summary

Impact: Spoofing. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.

I am running SharePoint Server 2016. Do the updates for SharePoint Enterprise Server 2016 also apply to the version I am running?
Yes. The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers running either version should install the security update to be protected from this vulnerability.

Security updates
16.0.20326.20190 — https://support.microsoft.com/help/5002927

Vulnerabilities 1

Medium 4.6

CVE-2026-88209

Microsoft Office SharePoint Spoofing Vulnerability

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.

Microsoft Microsoft SharePoint Server Subscription Edition

Oct 13, 2026

Revision history

2026-10-13 #1
Information published.

References

CVE-2026-88209 Microsoft Office SharePoint Spoofing Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-88209
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss