[German]As of June 29, 2021, Microsoft has released a special update (D-Week) for Windows 10 versions 2004, 20H2 and 21H1. This update, which is not rolled out via Windows Update, is intended to fix possible problems with opening and rendering PDF files in Internet Explorer 11 or in apps.
The out-of-band update KB5004760 aims to fix a problem that prevents PDF files from being opened in Internet Explorer 11 or in apps. However, the bug only occurs if they use the 64-bit version of the WebBrowser control. A second fixed bug is that a PDF file may only render as a gray background in the Adobe Acrobat plug-in.
The June 29, 2021 update upgrades the respective builds to 19041.1082 (Windows 2004), 19042.1082 (Windows 20H1), and 19043.1082 (Windows 21H1). This update is optional and installation should only be considered if the described errors occur on machines. Therefore, Microsoft does not provide the patch via Windows Update, but only offers a download from the Microsoft Update Catalog.
If administrators have to distribute the update to clients via WSUS, the downloaded update should be imported. When installing the update manually, make sure that the cumulative update KB5003173 from May 11, 2021 is already installed. The background is that Microsoft already integrates the required servicing stack updates (SSUs) in the mentioned Windows 10 build. I had reported about this problem in the blog post Windows 10: Microsoft confirms issues with June 2021 security update. Hints on how to uninstall the update via DISM, as well as details on known issues, can be found in KB article KB5004760.
Microsoft has also made direct improvements to the update client for Windows 10 to improve its reliability.
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