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PowerShell Script Signing Issues After November 2026 Update

PowerShell Script Signing Issues After November 2026 Update

First seen 14 Nov 2026, 18:13 UTC • •
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ThreatCluster AI
ThreatCluster •November 14, 2026 at 18:14 UTC
  • •Microsoft's update KB5132061 enforces stricter PowerShell script signature validation.
  • •Scripts with malformed UTF-8 encoding now fail verification and report as unsigned.
  • •No CVE is associated with this change, and no opt-out option is available.

Microsoft's November 10, 2026, Windows update KB5132061 introduced stricter validation for signed PowerShell scripts, causing some previously valid scripts to fail verification. This change affects scripts with malformed UTF-8 encoding, which now report as unsigned. Microsoft confirmed that no CVE is associated with this update, and there is no opt-out option available. Affected systems include Windows 11 versions 23H2 to 26H2, Windows 10 Enterprise LTSC 2021, and Windows Server 2016 to 2025. Administrators are advised to review and re-sign affected scripts, ensuring they are saved as UTF-8 with a byte-order mark. The update has implications for environments enforcing strict script signing, such as scheduled tasks and deployment pipelines, where unsigned scripts will not execute.

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Updated 6h ago How this analysis works

Timeline

2026-11-10
Windows update KB5132061 released
Microsoft released an update that changed PowerShell's script signature validation, affecting many scripts.
Cyberkendra
2026-11-12
Users report issues with signed scripts
Following the update, users began reporting that previously signed PowerShell scripts were failing verification.
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Common questions

Which Windows versions are affected?
The update affects Windows 11 versions 23H2 to 26H2, Windows 10 Enterprise LTSC 2021, and Windows Server 2016 to 2025.
What should I do if my scripts are failing?
Review your scripts, ensure they are saved as UTF-8 with a byte-order mark, and re-sign them.
Is there a workaround for this issue?
Currently, there is no opt-out option or workaround provided by Microsoft for this update.