January 23, 2020—KB4534308 (OS Build 17134.1276)

This non-security update includes quality improvements. Key changes include:

• Addresses an issue with using Web Account Manager to sign in to Office Apps. 
• Addresses an issue with download notifications that have multiple short-duration tabs and redirects. 
• Addresses an issue with a memory leak in ctfmon.exe that occurs when you refresh an application that has an editable box. 
• Addresses an issue with the Windows Out of Box Experience (OOBE) phase of setup for a new device. When you use the Input Method Editor (IME) for Chinese, Japanese, or Korean languages, you might not be able to create a local user account. 
• Addresses an issue with the multifactor unlock policy of Windows Hello for Business, which fails to show the default option to sign in on Windows 10 devices. 
• Addresses an issue that prevents computer objects from being added to local groups using the Group Policy Preference “Local Users and Groups”. The Group Policy Editor returns the error message, “The object selected does not match the type of destination source. Select again.” 
• Addresses an issue that prevents Internet Explorer from opening when Microsoft User Experience Virtualization (UE-V) is being used to roam many favorites. 
• Improves the reliability of the UE-V AppMonitor. 
• Addresses an issue that might prevent a user’s settings from syncing across devices. 
• Addresses an issue that might cause high CPU consumption in Microsoft Defender Advanced Threat Protection when using Microsoft Teams. 
• Addresses an issue that causes the Local Security Authority Subsystem Service (LSASS) process to stop working when you sign in using an updated user principal name (UPN) (for example, changing UserN@contoso.com to User.Name@contoso.com). The error code is, “0xc0000005 (STATUS_ACCESS_VIOLATION).” 
• Addresses an issue that causes a connection secured by IP security (IPSec) Internet Key Exchange Version 1 (IKEv1) to consume multiple, short-lived security associations (SA) instead of utilizing one until it expires. 
• Addresses an issue with AppContainer firewall rules that leak when guest users or mandatory user profile users sign in and sign out from Windows Server. 
• Addresses an issue that uses an incorrect number of bytes to perform backups across partitions; this causes backups to fail even when there is adequate space. 
• 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 in which netdom.exe fails to correctly identify trust relationships when an unconstrained delegation is explicitly enabled by adding bitmask 0x800 to the trust object. The bitmask setting is required because of security changes to the default behavior of unconstrained delegations in Windows updates released on or after July 8, 2019. For more information, see KB4490425 and 6.1.6.7.9 trustAttributes. 
• Addresses an issue that might cause the Application Virtualization (App-V) Streaming Driver (appvstr.sys) to leak memory when you enable Shared Content Store (SCS) mode.
• Addresses an issue that corrupts a log file when a storage volume is full and data is still being written to the Extensible Storage Engine Technology (ESENT) database.

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