January 12, 2021—KB4598242 (OS Builds 19041.746 and 19042.746)

EXPIRATION NOTICE****IMPORTANT As of 9/12/2023, this KB is only available from Windows Update. It is no longer available from the Microsoft Update Catalog or other release channels. We recommend that you update your devices to the latest security quality update.

**UPDATED 1/12/21
REMINDER **Adobe Flash Player went out of support on December 31, 2020. For more information, see Adobe Flash end of support on December 31, 2020. Flash content will be blocked from running in Flash Player beginning January 12, 2021. For more information, see Adobe Flash Player EOL General Information Page.

11/17/20
For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. To view other notes and messages, see the Windows 10, version 2004 update history home page.NoteFollow @WindowsUpdate to find out when new content is published to the release information dashboard.

Highlights

• Updates to improve security when using external devices, such as game controllers, printers, and web cameras.
• Updates to improve security when Windows performs basic operations.

Improvements and fixes

__

Windows 10, version 20H2

This security update includes quality improvements. Key changes include:

• This build includes all the improvements from Windows 10, version 2004.
• No additional issues were documented for this release.

__

Windows 10, version 2004

NoteThis release also contains updates for Microsoft HoloLens (OS Build 19041.1134) released January 13, 2021. Microsoft will release an update directly to the Windows Update Client to improve Windows Update reliability on Microsoft HoloLens that have not updated to this most recent OS Build.

This security update includes quality improvements. Key changes include:

• Addresses a security vulnerability issue with HTTPS-based intranet servers. After installing this update, HTTPS-based intranet servers cannot, by default, use a user proxy to detect updates. Scans using these servers will fail if you have not configured a system proxy on the clients. If you must use a user proxy, you must configure the behavior using the policy “Allow user proxy to be used as a fallback if detection using system proxy fails.” To ensure the highest levels of security, also use Windows Server Update Services (WSUS) Transport Layer Security (TLS) certificate pinning on all devices. This change does not affect customers who are using HTTP WSUS servers. For more information, see Changes to scans, improved security for Windows devices.
• Addresses a security bypass vulnerability that exists in the way the Printer Remote Procedure Call (RPC) binding handles authentication for the remote Winspool interface. For more information, see KB4599464.
• Security updates to Windows App Platform and Frameworks, Windows Media, Windows Fundamentals, Windows Kernel, Windows Cryptography, Windows Virtualization, Windows Peripherals, and Windows Hybrid Storage Services.

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 ImprovementsMicrosoft 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 updateSymptom	Workaround
When using the Microsoft Japanese Input Method Editor (IME) to enter Kanji characters in an app that automatically allows the input of Furigana characters, you might not get the correct Furigana characters. You might need to enter the Furigana characters manually.Note The affected apps are using theImmGetCompositionString() function.	This issue is resolved in KB5005101.
How to get this updateBefore installing this updateMicrosoft 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 (KB4598481) will be offered to you automatically. To get the standalone package for the latest SSU, search for it in the Microsoft Update Catalog.Release Channel	Available
—	—
Windows Update and Microsoft Update	Yes
Microsoft Update Catalog	No
Windows Server Update Services (WSUS)	No
File informationFor a list of the files that are provided in this update, download the file information for cumulative update 4598242.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.