September 8, 2020—KB4577015 (OS Build 14393.3930)

Applies to: Windows 10 Version 1607Windows Server 2016


  • Updates time zone information for the Yukon, Canada. 
  • Updates to improve security when using Microsoft Office products.
  • Updates to improve security in the Microsoft Store.
  • Updates to improve security when Windows performs basic operations.
  • Updates for storing and managing files.

Improvements and fixes

This security update includes quality improvements. Key changes include:

  • Provides the ability to set a Group Policy that displays only the domain and username when you sign in. 
  • Updates time zone information for the Yukon, Canada. 
  • Addresses an issue that prevents the Event Viewer from properly saving filtered events. 
  • Addresses an issue with object performance counters. 
  • Addresses an issue that sometimes prevents AppLocker from running an application whose publisher rule allows it to run.
  • Addresses an issue that causes delays during shutdown when running the Microsoft Keyboard Filter Service.
  • Addresses a security vulnerability issue with user proxies and HTTP-based intranet servers. After installing this update, HTTP-based intranet servers cannot leverage a user proxy by default to detect updates. Scans using these servers will fail if the clients do not have a configured system proxy. If you must leverage a user proxy, you must configure the behavior using the Windows Update policy “Allow user proxy to be used as a fallback if detection using system proxy fails.” This change does not affect customers who secure their Windows Server Update Services (WSUS) servers with the Transport Layer Security (TLS) or Secure Sockets Layer (SSL) protocols. For more information, see Improving security for devices receiving updates via WSUS.
  • Addresses an issue with evaluating the compatibility status of the Windows ecosystem to help ensure application and device compatibility for all updates to Windows. 
  • Addresses an issue that might prevent a client from reconnecting to a previous RemoteApp session unless an administrator closes the session on the server.
  • Security updates to Windows App Platform and Frameworks, Microsoft Graphics Component, Windows Input and Composition, Windows Media, Windows Shell, the Microsoft Store, Windows Cloud Infrastructure, Windows Fundamentals, Windows Kernel, Windows Virtualization, Windows Storage and Filesystems, the Microsoft Scripting Engine, and the Microsoft JET Database Engine.

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

For more information about the resolved security vulnerabilities, please refer to the Security Update Guide.

Known issues in this update

Symptom Workaround
After installing KB4467684, the cluster service may fail to start with the error “2245 (NERR_PasswordTooShort)” if the group policy “Minimum Password Length” is configured with greater than 14 characters.

Set the domain default "Minimum Password Length" policy to less than or equal to 14 characters.

Microsoft is working on a resolution and will provide an update in an upcoming release.

Accessing the Security Options data view in the Group Policy Management Editor (gpedit.msc) or Local Security Policy Editor (secpol.msc) might fail with the error "MMC has detected an error in a snap-in. It is recommended that you shut down and restart MMC" or “MMC cannot initialize the snap-in”. This occurs from the MMC window, when the console tree is expanded in the following sequence: select Computer Configuration, then Policies, then Windows Settings, then Security Settings, then Local Policies, then Security Options.

The resulting error dialog provides options to continue using the Management Console to view other nodes normally. Note: This issue does not affect the application of the Security Options or any other Group Policy Objects (GPOs) to devices in your environment.

This issue is resolved in KB4580346.

How to get this update

Before installing this update

Microsoft strongly recommends you install the latest servicing stack update (SSU) for your operating system before installing the latest cumulative update (LCU). SSUs improve the reliability of the update process to mitigate potential issues while installing the LCU and applying Microsoft security fixes. For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.

If you are using Windows Update, the latest SSU (KB4576750) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog

Install this update

Release Channel Available Next Step
Windows Update and Microsoft Update Yes None. This update will be downloaded and installed automatically from Windows Update.
Microsoft Update Catalog Yes To get the standalone package for this update, go to the Microsoft Update Catalog website.
Windows Server Update Services (WSUS) Yes

This update will automatically sync with WSUS if you configure Products and Classifications as follows:

Product: Windows 10

Classification: Security Updates


File information

For a list of the files that are provided in this update, download the file information for cumulative update 4577015