KB5066791: Fixed: An issue that affects PowerShell

October 14, 2025—KB5066791 (OS Builds 19044.6456 and 19045.6456)

This security update includes fixes and quality improvements that are part of the following updates:

• September 9, 2025—KB5065429 (OS Builds 19044.6332 and 19045.6332)
• September 25, 2025—KB5066198 (OS Build 19045.6395) Preview

The following is a summary of the issues that this update addresses when you install this update. If there are new features, it lists them as well. The bold text within the brackets indicates the item or area of the change we are documenting.

[Input and Composition]

• Fixed: An issue with the Chinese Input Method Editor (IME). Private Unicode characters were shown incorrectly and did not meet GB18030 standard.
• Fixed: An issue that affects USER32 Edit controls. Surrogate pairs appear as empty boxes when text fields reach their length limit.

[Windows Remote Management (WinRM)]

• Fixed: An issue that affects PowerShell Remoting and WinRM in which commands time out after 600 seconds.

[Licensing]

• New! This update introduces a servicing stack update (SSU) which incorporates an updated certificate chain to improve Azure environment validation. For more information, see the servicing stack update section.

[Fax modem driver]

• This update removes the ltmdm64.sys driver. Fax modem hardware dependent on this specific driver will no longer work in Windows.

If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.