IMPORTANT Because of minimal operations during the holidays and the upcoming Western new year, there won’t be a preview release (known as a “C” release) for the month of December 2020. There will be a monthly security release (known as a “B” release) for December 2020. Normal monthly servicing for both B and C releases will resume in January 2021.
For more information about the various types of Windows updates, such as critical, security, driver, service packs, and so on, please see the following article. To view other notes and messages, see the Windows 10, version 1903 update history home page.
Note Follow @WindowsUpdate to find out when new content is published to the release information dashboard.
- Updates the 2020 DST start date for the Fiji Islands to December 20, 2020.
- Updates to improve security when using Microsoft Office products.
- Updates to improve security when using input devices such as a mouse, keyboard, or pen.
- Updates to improve security when Windows performs basic operations.
Improvements and fixes
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 new Security Update Guide website.
Windows Update Improvements
Microsoft has released an update directly to the Windows Update client to improve reliability. Any device running Windows 10 configured to receive updates automatically from Windows Update, including Enterprise and Pro editions, will be offered the latest Windows 10 feature update based on device compatibility and Windows Update for Business deferral policy. This doesn't apply to long-term servicing editions.
Known issues in this update
System and user certificates might be lost when updating a device from Windows 10, version 1809 or later to a later version of Windows 10. Devices will only be impacted if they have already installed any Latest cumulative update (LCU) released September 16, 2020 or later and then proceed to update to a later version of Windows 10 from media or an installation source which does not have an LCU released October 13, 2020 or later integrated. This primarily happens when managed devices are updated using outdated bundles or media through an update management tool such as Windows Server Update Services (WSUS) or Microsoft Endpoint Configuration Manager. This might also happen when using outdated physical media or ISO images that do not have the latest updates integrated.
Note Devices using Windows Update for Business or that connect directly to Windows Update are not impacted. Any device connecting to Windows Update should always receive the latest versions of the feature update, including the latest LCU, without any extra steps.
If you have already encountered this issue on your device, you can mitigate it within the uninstall window by going back to your previous version of Windows using the instructions here. The uninstall window might be 10 or 30 days depending on the configuration of your environment and the version you’re updating to. You will then need to update to the later version of Windows 10 after the issue is resolved in your environment. Note Within the uninstall window, you can increase the number of days you have to go back to your previous version of Windows 10 by using the DISM command /Set-OSUninstallWindow. You must make this change before the default uninstall window has lapsed. For more information, see DISM operating system uninstall command-line options.
We are working on a resolution and will provide updated bundles and refreshed media in the coming weeks.
After installing this update on domain controllers (DCs) and read-only domain controllers (RODCs) in your environment, you might encounter Kerberos authentication and ticket renewal issues. This is caused by an issue in how CVE-2020-17049 was addressed in these updates.
Note This issue only affects Windows Servers, Windows 10 devices and applications in enterprise environments.
|This issue is resolved in KB4594443.|
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.
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, version 1903 and laterClassification: Security Updates
For a list of the files that are provided in this update, download the file information for cumulative update 4586786.
Note Some files erroneously have “Not applicable” in the “File version” column of the CSV file. This might lead to false positives or false negatives when using some third-party scan detection tools to validate the build.