こんにちは、鯨井貴博@opensourcetechです。
5/13にVirtualboxの新バージョン、4.3.28がリリースされました！
https://www.virtualbox.org/wiki/Downloads 
変更履歴は、以下の通りとなります。
https://www.virtualbox.org/wiki/Changelog
多くの修正がされていますので、利用されている方はぜひバージョンアップを！！
- VMM: fixed a Guru Meditation when rebooting certain guests (for example Solaris doing fast reboot) by fixing the implementation for INIT IPI
- VMM: added some information for diagnosing rare VERR_VMX_INVALID_VMXON_PTR Guru Meditations (VT-x only)
- GUI: HID LEDs sync: prevent synchronization if VM window has no focus (Windows and Mac OS X hosts only)
- GUI: fixed drag and drop moving the cursor between guest screens on certain hosts
- 3D: fixed a crash on restoring the VM state on X11 hosts (bug #12737)
- 3D: fixed a crash on Linux guest shutdown (bug #12772)
- VRDP: fixed incompatibility with rdesktop 1.8.3
- VRDP: fixed listening for IPv6 on some systems (bug #14038)
- Storage: don't crash if creating an asynchronous I/O context fails (e.g. when starting many VMs) and show a proper error message
- Floppy: several fixes
- Audio: improved the behavior of the volume control for the HD audio device emulation
- USB: increase the number of supported drivers from 3 to 5 (Windows hosts only)
- PS/2 keyboard: synchronize the LED state on VM restore (Windows and Mac OS X hosts only)
- NAT Network: when running multiple NAT networks with multiple VMs, only stop the respective services when stopping VMs (bug #14090)
- NAT: don't kill UDP bindings on ICMP errors (bug #13475)
- NAT: bandwidth limit now works properly with NAT (bug #11485)
- BIOS: fixed the returned size value of the VBE 2.0 PMI function 0Ah (4.2.0 regression; bug #14096)
- Guest Control: fixed parameter quoting in Windows guests (bug #13157)
- Webcam passthrough improvements for Linux (V4L2) hosts to support more webcam models
- API: don't fail starting a VM with VBOX_E_INVALID_OBJECT_STATE under certain conditions (bug #13617)
- API: be more verbose on VBOX_E_INVALID_OBJECT_STATE if a medium is attached to a running VM (bug #13560)
- API: fixed a bug which could result in losing certain screen resize events with multi-monitor guests
- rdesktop-vrdp: fixed path to the keymaps (bug #12066)
- rdesktop-vrdp: switch to version 1.8.3
- Windows hosts: more hardening fixes (e.g. bugs #14051, #14052)
- Linux hosts: another fix for activated SMAP on Linux 3.19 and newer (Broadwell and later; bug #13961)
- Linux hosts: Linux 4.1 compile fix (bug #14081)
- Solaris hosts: fixed using of VNIC templates with Crossbow based bridged networking to be compatible with vanity interface names
- Mac OS X hosts: fixed crash during VM termination under rare circumstances
- Windows Additions/WDDM: improved video memory utilization and allow more/bigger guest screens with large resolutions (including HiDPI)
- X11 Additions: prevent flickering when updating mouse cursor
- Solaris Additions: fixed incorrect usage of 'prtconf' while installing Guest Additions (Solaris 10 only)
