If you've already upgraded your PC to Windows 10 version 2004, you'll get KB4557957, bringing the build number to 19041.329, and these are the highlights:
Updates an issue that prevents you from using some voice commands in Windows Mixed Reality when the default Windows language is Canadian or Australian English. Improves the reliability of the keywords used for voice assistants, including Cortana. Updates to improve security when using Internet Explorer and Microsoft Edge. Updates to improve security when Windows performs basic operations. Updates to improve security when using Microsoft Office products. Updates to improve security when using external devices (such as game controllers, printers, and web cameras) and input devices (such as a mouse, keyboard, or stylus). Improves security in Microsoft Xbox and the Microsoft Store. Updates for verifying usernames and passwords. Updates for storing and managing files.
Here's the full list of improvements and fixes:
Addresses an issue that prevents users from updating .msi files from a network folder. Addresses an issue that prevents you from using some voice commands in Windows Mixed Reality when the preferred Windows display language is English (Canada) or English (Australia). Improves the reliability of voice assistants that use Windows voice activation (Settings > Privacy > Voice Activation) for keywords. Improves the reliability of Cortana's voice activation when using the “Cortana” keyword on devices that support low-power keywords. Security updates to the Microsoft Scripting Engine, Microsoft Edge, Internet Explorer, Windows App Platform and Frameworks, Windows Media, Windows Kernel, Microsoft Graphics Component, Windows Input and Composition, Windows Shell, Windows Silicon Platform, Microsoft Xbox, the Microsoft Store, Windows Cloud Infrastructure, Windows Fundamentals, Windows Management, Windows Authentication, Windows Cryptography, Microsoft HoloLens, Windows Virtualization, Windows Peripherals, Windows Storage and Filesystems, Windows File Server and Clustering, Windows Hybrid Storage Services, the Microsoft JET Database Engine, and the Windows Update Stack.