Microsoft has acknowledged a significant issue with the .NET Framework updates from August 2026, causing disruptions in printing and PDF export functionalities in certain applications, particularly those using the Windows Presentation Foundation (WPF) UI framework. After installing the update, some WPF applications may encounter a System.IO.FileFormatException when printing or generating PDF/XPS content with specific fonts, including Calibri. This issue affects various platforms, including Windows 10, Windows 11, and Windows Server editions from 2012 to 2025. Microsoft has provided a temporary workaround involving the Switch.MS.Internal.TtfDelta.DisableCmapAndSbitOverflowProtection AppContext switch, but cautions that it may expose systems to vulnerabilities. This situation is reminiscent of a similar incident in February 2021, where WPF applications and Visual Studio experienced crashes after Windows 10 cumulative updates. Additionally, on the same day, Microsoft offered a workaround for another issue caused by Windows 11 updates that led to crashes in certain games.