Windows Update has caused problems with printing and PDF export in some applications.
A Windows Update released on August 12, 2026, caused an issue where printing and exporting to PDF stopped working in some applications. Microsoft has acknowledged this issue and provided a workaround.
August 11, 2026 - KB5120698 Cumulative Update for .NET Framework 3.5 and 4.7.2 for Windows 10 Version 1809 and Windows Server 2019 | Microsoft Support
Microsoft: August updates break printing, PDF export in WPF apps
https://www.bleepingcomputer.com/news/microsoft/microsoft-august-updates-break-printing-pdf-export-in-wpf-apps/
According to Microsoft, after installing the .NET Framework update released as part of Windows Update, some applications may fail to print or generate PDF/XPS content that uses certain fonts, including Calibri , due to a System.IO.FileFormatException error.
The applications experiencing this problem use the Windows Presentation Foundation (WPF) UI framework.
This issue affects Windows client releases, including the latest versions of Windows 10 and Windows 11, as well as Windows Server versions from Windows Server 2012 to Windows Server 2025.
Microsoft is 'investigating' the issue and has suggested enabling the 'Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch' in the app configuration file as a workaround. However, Microsoft points out that using this switch disables security protection introduced in the August 2026 update, potentially increasing the likelihood of being exposed to the vulnerability addressed by that update, and adds, 'We recommend using this workaround only when necessary, as it is a temporary solution to address this issue.'
This Windows Update has also caused another problem, resulting in some games crashing.
Microsoft warns that 'August Windows update may cause problems with games' - GIGAZINE
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