Microsoft released security updates for .Net on August 11 to address six unique vulnerabilities. After installing the update on supported systems, users may notice printing issues.
Microsoft confirmed the issue in the release notes for the update. There, the company notes that “some WPF applications may fail with a System.IO.FileFormatException when printing or generating PDF/XPS content that uses certain fonts, including Calibri” after installing the update.
WPS refers to Windows Presentation Foundation, “UI framework that’s resolution-independent and uses a vector-based rendering engine, built to take advantage of modern graphics hardware.”
The issue is under investigation currently and there is no workaround for users at the time. App developers, who use WPF, may make use of a workaround to mitigate the issue.
Doing so will “disable security productions introduced in the August 2026 update”, which may increase the exposure to the addressed vulnerabilities.
Uninstalling the update could also restore printing functionality, but I have not tested this as I could not replicate the issue on my devices. Considering that disabling the security fixes is a recommended workaround by Microsoft, I’d say there is a good chance that this could work.