https://www.virtualbox.org/wiki/Changelog-6.1#v0

VirtualBox 6.1.0 (released December 10 2019)

This is a major update. The following major new features were added:

Implemented support for importing a virtual machine from Oracle Cloud Infrastructure
Extended support for exporting a virtual machine to Oracle Cloud Infrastructure, allowing the creation of multiple virtual machines without re-uploading. Also added option to export a VM to the cloud using the more efficient variant "paravirtialized", and to specify free-form tags for cloud images
Virtualization core: Support for nested hardware-virtualization on Intel CPUs (starting with 5th generation Core i, codename Broadwell), so far tested only with guest running VirtualBox
Graphics: New style 3D support (with VBoxSVGA and VMSVGA) remains, old style 3D support (with VBoxVGA) has been completely removed
Shared Clipboard: Implemented experimental support for file transfers (Windows hosts/guests only at the moment). Needs to be enabled via VBoxManage (disabled by default). In addition, the following items were fixed and/or added:
Virtualization core: Drop recompiler, i.e. running VMs now needs a CPU supporting hardware virtualization
Runtime: Works now on hosts with many CPUs (limit now 1024)
Appliance and Cloud Import: Add field for defining firmware type (not part of OVF spec and thus manual in the Appliance case, for OCI it is automatically taken from the instance information)
GUI: Improved the VISO creation and file manager dialogs
GUI: Virtual machine list of VirtualBox Manager was improved. Machine groups are now more obvious visually and VM search functionality has been improved. Global Tools element can now be pinned in place, to avoid scrolling it with rest of machine list
GUI: Virtual machine details pane is now extended with embedded editors for selected VM attributes, allowing user to edit them on-the-fly byi clicking corresponding hyper-links without opening VM settings dialog
GUI: Details pane provides more complete information
GUI: Internal medium enumeration routines were optimized to reduce the load and optimize the performance in cases when user have lots of media registered. Also, we again allowed to add existing media (and create new) via Virtual Media Manager
GUI: More consistent medium selection (both showing known images and allowing to select using the file picker)
GUI: VM storage settings page was adjusted a bit in usability regard. User is now allowed to change controller bus type and can move attachments between the controllers by using drag and drop
GUI: Storage and Network settings pages bug-fixes and usability optimization
GUI: Added a new soft (virtual) keyboard enabling arbitrary keyboard input to guests, including multimedia keys
GUI: Fixed crash in cloud related wizards when accessibility functionality was enabled
GUI: Show VM CPU load as part of status bar CPU indicator
GUI: Improved and extended the Session Information dialog
GUI: Fixed/improved mouse pointer scaling
GUI: Some issues related to mouse integration cursor scaling were addressed (bug #14366), more to go
GUI: Fix and unify geometry save/restore in various dialogs
GUI: Added the missing restriction options for disabling new functionality such as the VISO creator
GUI: Popup messages mouse click fix
Graphics: Remove 3D support for VBoxVGA (old one deprecated with 6.0)
Graphics: Additional texture format support on Windows host
Graphics: Improved fix for flickering on Windows host
Input: Added support for horizontal scrolling in the PS/2 mouse device using the IntelliMouse Explorer protocol. Note that this support is automatically used by Linux guests but not by Windows guests
vboximg-mount: Experimental support for direct read-only access to NTFS, FAT and ext2/3/4 filesystems inside a disk image without the need for support on the host
vboximg-mount: Now also available on Linux host
Storage: Experimental support for virtio-scsi, for both hard disks and optical drives (including boot support in BIOS)
Storage: For optical drive emulation fix empty host drive crash
USB: Improvements for EHCI controller implementation
USB: Filter can now specify port path, uniquely identifying a port in a system
NAT: Fix TFTP OACK response, send only if request has options
NAT Network: Use non-blocking sockets on Linux for accepted incoming connections (port forwarding)
PCnet-ISA: Added new network adapter type, currently CLI only
Audio: Allow changing the host audio backend while the VM is in saved state
ACPI: Report NVMe controller
VGA: Improve hardware and BIOS compatibility
VBoxSVGA/VMSVGA: Support YUV2 and related texture formats with hosts using OpenGL (macOS and Linux), which accelerates video playback when 3D is enabled by delegating the color space conversion to the host GPU
VBoxSVGA/VMSVGA: Several drawing fixes for the 3D case
VMSVGA 3D: Fixed OpenGL compressed textures
VBoxManage: More cloud functionality coverage, e.g. starting a cloud instance
VBoxManage: As part of the guest control feature support moving multiple source files/directories to a target directory
Guest Control/VBoxManage: Added support for specifying multiple sources when renaming guest files
VBoxManage: Show "unrestricted guest" and "nested HW virtualization" CPU features when listing the host information
API: Reduce the amount of leftovers from Move VM function
Shared Clipboard: Implemented experimental support for file transfers for Linux hosts on Windows guests (disabled by default)
SMBIOS: Store system UUID in little endian format which is the default for new VMs, while existing VMs stick to the old VirtualBox behavior of storing them in big endian format for backwards compatibility to avoid breaking the activation status of Windows VMs
VBoxSDL frontend: Fixed running on Windows hosts
macOS host: Fix VM crashes (most visible on macOS Catalina)
Linux host: Improve vboxweb systemd service dependency information
Linux host: Drop PCI passthrough, the current code is too incomplete (cannot handle PCIe devices at all), i.e. not useful enough
Linux host and guest: Support Linux 5.4 (bug #18945)
Linux host and guest: Force disabling of kernel module signing during build (user can do it afterwards)
Windows host: When possible, distinguish USB devices by port number; helps with accurate capturing of devices when multiple otherwise identical devices are connected
Windows Guest Additions: Many fixes for drawing problems in the driver for VBoxSVGA
Windows Guest Additions: Fixes for legacy VBoxVGA adapter, restore previously working cases
Windows Guest Additions: Restore VHWA functionality for VBoxSVGA
Windows guest: DXVA implementation for WDDM driver
Documentation: Updated supported host operating systems, added few new manual pages (more to come later)
EFI: Switch to newer firmware code base and add NVRAM support, should improve compatibility with OSes significantly
EFI: Added support for booting from APFS
EFI: Added support for non-standard SATA and NVMe boot device paths created by OS X
EFI: Modified updated EFI code base to support older OS X guests again

Linux host: Drop PCI passthrough, the current code is too incomplete (cannot handle PCIe devices at all), i.e. not useful enough

This is a significant (non-) feature for BOINC. No GPUs.

https://www.virtualbox.org/wiki/Changelog-6.1#v4

VirtualBox 6.1.4 (released February 19 2020)

This is a maintenance release. The following items were fixed and/or added:

Virtualization core: Fixed a rare issue with ICEBP instruction causing guru meditations on Intel hosts (6.1.0 regression; bug #19171)
Virtualization core: Fixed macOS Catalina guests failing to boot after upgrading to 10.15.2 onwards (bug #19188)
GUI: recent NLS integration and bug fixes for GUI and Qt translation tags
USB: Fix isochronous transfers to the VM for xHCI
Serial: Fix buffer handling, avoiding receiving stale data when the receive queue is flushed (bug #18671)
Serial: Improve host serial port passthrough handling on Windows host
VBoxManage: Restore old --clipboard option for modifyvm command
macOS host: Use hardened runtime and request the needed entitlements, meeting latest notarization rules which also required moving VirtualBoxVM executable
macOS host: Update osxfuse to v3.10.4
Windows host: Update Italian translation of installer
Windows host: Improve shared folder compatibility with POSIX append semantic (bug #19003)
Windows host: Restore the ability to run VMs through Hyper-V, at the expense of performance
Linux guest: Support Linux 5.5 (bug #19145)
Linux guest: Shared folder fix for loopback mounting of images
BIOS: Always report non-ATA disks as ready
BIOS: Report EFI support through DMI table (bug 19144)
VGA BIOS: Reduce stack space usage for INT 10h handlers