VirtualBox v4.3.20 is released. VirtualBox is a general-purpose full virtualizer for x86/x64 hardware. Targeted at server, desktop and embedded use, it is now the only professional-quality virtualization solution that is also Open Source Software.

VirtualBox v4.3.20 Changelog:
VirtualBox 4.3.20 is a maintenance release. The following items were fixed and/or added since VirtualBox 4.3.18:
VMM: fixed reboot hang of 32-bit Windows SMP guests (bug #13319, #13462)
VMM: proper Math Fault handling with certain legacy guests (bug #9042, AMD hosts)
VMM: fixed a Guru Meditation VINF_EM_TRIPLE_FAULT on older CPUs that don't support MSR-bitmaps (VT-x only; bugs #13034, #13125, #13311, #13425, #13426, #13463, #13585)
GUI: fix 3D overlay window re-parenting issue when VM goes to full screen mode on X11 hosts.
GUI: fix occasional loss of focus in full-screen mode on X11 host systems (4.3.16 regression)
GUI: Mac OS X: wizards should have Cancel button (bug #12541)
GUI: added a global option to prevent automatic raising of the new window by mouse move with multi-screen guests (bug #8878)
API: accept remote display port 0 as the default RDP port (bug #8534)
VBoxManage: fixed crash when executing showvminfo command under certain circumstances (bug #13190)
ACPI: fixed occasional Guru Meditations in ACPI timer code (4.3.18 regression; bug #13521)
EFI: improved performance of IDE disk access
EFI: fixed a bug in the EFI video driver which prevented Windows to boot in UEFI mode (bug #12022)
EFI: properly announce the amount of RAM for big VMs (bugs #11103 and #13211)
Storage: fixed a crash under certain circumstances when a medium was ejected from a drive attached to the SATA controller without inserting a new medium before pausing or closing the VM (4.3.16 regression)
Storage: fixed an interrupt acknowledge issue causing hanging guests or slower I/O (4.3.18 regression)
Storage: fixed broken resume after the VM was suspended due to a full disk if host I/O caching is used
Storage: fixed a Guru Meditation under certain conditions when using the DevLsiLogic controller with VMs running in raw mode (4.3 regression; bugs #12254, #12655, #12709, #12774, #12886)
Guest Control: fixed a bug which might lead to a crash during recursive copy
SDK: Java COM bindings fixes
iPXE: enable the HTTP download protocol (bug #13628)
Runtime: do not use a fixed stack size creating temporary threads during initialization (bug #13038)
Windows hosts: fixed more startup problems on certain Windows hosts due to conflicts with anti-virus software; better error reporting (4.3.14 regression; bug #13187)
Windows hosts: fixed DirectSound host audio failure under certain conditions (bug #13418)
Windows hosts: fixed additional cases of 4.3.14 regression whereby AltGr stopped working for some people (bug #13216)
Windows Additions: preserve guest monitor layout when resizing Windows 7 or newer guests
Linux Additions: Linux 3.18 compile fixes (bug #13515)

Download: VirtualBox v4.3.20
Source: Here