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

- GUI: show actual VM uptime in the session information window
- Audio: re-enabled speakers for Mac OS X guests (5.1.0 regression; bug #15611)
- Audio: fixed crashes under certain conditions
- USB: fixed a hang under certain conditions
- USB: fixed a hanging guest under certain conditions (bug #15747)
- PIIX4: implemented dummy SMBus controller to prevent annoying Linux kernel warnings about uninitialized SMBus base address (bug #9517)
- NVMe: several fixes to improve stability, fixed a crash while saving a VM state
- VMDK: Fixed an issue creating fixed size images with certain sizes and the Split2G option enabled (bug #15748)
- VHDX: fixed cloning images with VBoxManage clonehd (bug #14288)
- Storage: Fixed broken bandwidth limitation when the limit is very low (bug #14982)
- EFI: fixed sending debug messages in the EFI firmware if a serial port is enabled (bug #12161)
- OVF: when importing appliances, make sure that the version of the embedded VirtualBox-specific settings is processed, to get the default settings handling right
- VBoxManage: Don't try to set the medium type if there is no change (bug #13850)
- Linux installer: fixed some scripting issues (bugs #15701 and #15702)
- Linux installer: fixed a path issue on certain Linux distributions (bug #15717)
- Windows hosts: fixed corrupted mouse pointers with some Linux and Solaris guests (bug #15665)
- Linux Additions: made the video driver work on 32-bit guests with large video memory sizes (bug #15621)
- Linux Additions: made the video driver work on kernel 4.7 and later (bug #15769)
- Linux Additions: converted a failure message to an informational one when drivers could not be stopped during upgrade (bug #15692)
- Linux Additions: made the video driver work around an X server bug which cause screen refresh to stop (bug #15511)
- Windows Additions: auto-resizing fixes for Windows 10 guests (bug #15257)
- Windows Additions: fixed VBoxTray problems with Windows 2000 (bug #15661)