This is a maintenance release. The following items were fixed and/or added:
VMM: Fixed random memory corruption and XMM register state corruption inside the VM when Hyper-V is used (bug #19695)
VMM: Fixed VMSVGA 3D support with Linux guests when Hyper-V is used (bug #19884)
GUI: Fixed some Qt related crashes on macOS Big Sur
Oracle Cloud Infrastructure integration: Fixed network integration not working behind some proxies
USB: Mask out remote wake capability to avoid unresponsive devices
Audio: Fixed issues with audio playback after host goes to sleep (bug #18594)
Serial: Keep transferring data if the status line monitoring fails
Serial: Fixed blocking a re-connect when TCP mode is used (bug #19878)
HPET: Fixed inability of guests to use the last timer
VBoxManage: Fixed detection of system locale when running 'VBoxManage unattended install' without --locale (bug #19856)
macOS host: Installer on Big Sur is now reminding user that system has to be rebooted to load the installed KEXTs
Linux host and guest: Support kernel version 5.9 (bug #19845)
Linux guest: Workaround to improve resizing of 32-bit VMs with VMSVGA graphics controller, and do not try to use RandR version 1.3 due to bugs causing the X server to hang
Linux guest: Fixed VBoxService crashing in the CPU hot-plug service under certain circumstances during a CPU hot-unplug event (bugs #19902 and #19903)
Linux guest: Fixed Guest additions build for RHEL 8.3 beta (bug #19863)
Oracle VirtualBox 6.1.16 
