Windows 10 STIG Version Comparison
Windows 10 Security Technical Implementation Guide
There are 5 differences between versions v2 r1 (Nov. 13, 2020) (the "left" version) and v2 r2 (May 4, 2021) (the "right" version).
Check WN10-00-000015 was changed between these two versions. Green, underlined text was added, red, struck-out text was removed.
Windows 10 systems must have Unified Extensible Firmware Interface (UEFI) firmware and be configured to run in UEFI mode, not Legacy BIOS.
For virtual desktop implementations (VDIs) where the virtual desktop instance is deleted or refreshed upon logoff, this is NA. Verify the system firmware is configured to run in UEFI mode, not Legacy BIOS. Run "System Information". Under "System Summary", if "BIOS Mode" does not display "UEFI", this is finding.
UEFI provides additional security features in comparison to legacy BIOS firmware, including Secure Boot. UEFI is required to support additional security features in Windows 10, including Virtualization Based Security and Credential Guard. Systems with UEFI that are operating in Legacy BIOS mode will not support these security features.
Configure UEFI firmware to run in UEFI mode, not Legacy BIOS mode.