A font is a graphical representation of text that may include a different typeface, point size, weight, color, or design.
The Untrusted Font Blocking security feature provides a global setting to prevent programs from loading untrusted fonts. Untrusted fonts are any font installed outside of the C:\Windows\Fonts directory. This feature can be configured to be in 3 modes: On, Off, and Audit.
After you turn this feature on, or start using Audit mode, you can look at your event logs for details.
Users may still need apps that have problems because of blocked fonts, so it is suggested that you first run this feature in Audit mode to determine which fonts are causing the problems. After you figure out the problematic fonts, you can try to fix your apps in one of two ways: by directly installing the fonts into the %windir%/Fonts directory or by excluding the underlying processes (apps) and letting the fonts load. As the default solution, it is highly recommend that you install the problematic font. Installing fonts is safer than excluding apps because excluded apps can load any font, trusted or untrusted.
This tutorial will show you how to exclude specific apps from Untrusted Font Blocking for all users in Windows 10.