December 10, 2019-KB4533001 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10 Version 1809 and Windows Server 2019

Release Date:
December 10, 2019

Version:
.NET Framework 3.5 and 4.8

The December 10, 2019 update for Windows 10 Version 1809 and Windows Server 2019 includes cumulative reliability improvements in .NET 3.5 and 4.8. We recommend that you apply this update as part of your regular maintenance routines. Before you install this update, see the Prerequisites and Restart requirement sections.

Quality and reliability improvements

ASP.NET

ASP.NET now emits a SameSite cookie header when HttpCookie.SameSite value is "None" to accommodate upcoming changes to SameSite cookie handling in Chrome. As part of this change, FormsAuth and SessionState cookies  are also issued with SameSite = 'Lax' instead of the previous default of 'None', though these values can be overridden in web.config. Applications that use these cookies across sites – or with iframes – may see a loss of functionality that will require configuration updates to remedy.

For more information, refer to: https://docs.microsoft.com/en-us/aspnet/samesite/system-web-samesite.

WPF1

Addresses an issue where some Per-Monitor Aware WPF applications that host System-Aware or Unaware child-windows, and run on .NET 4.8, may occasionally encounter a crash with exceptionSystem.Collections.Generic.KeyNotFoundException.

CLR2

Addresses an issue where some ClickOnce applications or applications creating the default AppDomain with a restricted permission set may observe application launch or application runtime failures, or unexpected behaviors. The observable issue was the System.AppDomainSetup.TargetFrameworkName is null, leading to any quirks enabling reverting back to .NET Framework 4.0 behaviors.


1 Windows Presentation Foundation (WPF)
2 Common Language Runtime (CLR)

Known Issues in this update

There are no known issues with this update, however, this update resolves a previous known issue. This patch includes improvements to resolve a known issue discussed in KB4519565 that occurs after applying the October Preview of Quality Rollup for .NET Framework 4.8. To resolve this issue, install update for .NET Framework 4.8 for Windows 10 Version 1809 and Windows Server 2019 KB4533001.

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

  • 4533094 Description of the Cumulative Update for .NET Framework 3.5, 4.7.2 and 4.8 for Windows 10 Version 1809 and Windows Server 2019 (KB4533094)

How to obtain and install the update

Install this update

This update will be downloaded and installed automatically from Windows Update.

To get the standalone package for this update, go to the Microsoft Update Catalog website.

File information

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

Prerequisites

To apply this update, you must have .NET Framework 3.5 and 4.8 installed.

Restart requirement

You must restart the computer after you apply this update if any affected files are being used. We recommend that you exit all .NET Framework-based applications before you apply this update.

Update replacement information

This update replaces previously released updates 4520405 and 4524099.

How to obtain help and support for this update

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