Virtualbox 4.3.18 has been released 4 days ago with a lot of changes and bug fixes, below is the list of item were fixed and added on the new version of Virtualbox.

• VMM: fixed a potential misbehavior after restoring the A20 state from a saved state
• GUI: fixed full-screen mode mini-toolbar related regressions for different platforms and window managers (bug #13369)
• GUI: X11: fixed full-screen mode Unity panels quirk caused by mini-toolbar code changes in last release (bug #13365)
• GUI: X11: added possibility to use legacy full-screen mode as the new one can cause multi-screen issues under Unity, see the manual for more information (bug #13365)
• GUI: Mac OS X: fixed full-screen mode artifact causing black screen when 3D acceleration was enabled on 10.10 Yosemite hosts (bug #13448)
• GUI: Mac OS X: fixed regression in user-space swiping from/to VBox in full-screen mode
• GUI: Mac OS X: fixed issue with switching to VBox in full-screen mode through Alt+Tab and Mission Control
• Storage: fixed data corruption when resizing huge VHD images under certain circumstances (bug #11960)
• Storage: fixed a rare hang during startup when the BIOS enumerates the storage devices attached to the SATA controller
• Storage: follow the spec with AHCI interrupt acknowledge (bug #13474)
• Storage: fixed broken iSCSI authentication (4.3.14 regression, bugs #13386, #13435)
• NAT Network: properly parse port forwarding rules to allow UDP rules
• USB: fixed a crash on Linux hosts with older Linux kernels (bug #13400) and several other fixes
• ACPI: fixed ACPI timer anomalies (bug #12076)
• Guest Control: fixed a memory leak (bug #13434)
• Main: when removing a VM, do also remove the VBoxStartup.log file which might exist on Windows hosts (bug #13478)
• 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: propagate the process startup information to the child process (4.3.14 regression; bug #13243)
• Mac OS X hosts: don’t force using the discrete GPU (bug #11111)
• Windows Additions: some Windows 10 tweaks
• X11 guests: fix a bug handling video driver display properties which prevented GNOME Shell on Fedora 21 from starting
• Linux hosts / guests: fixed a few remaining warnings in the kernel log if memory allocation fails (bug #11171)

 
VirtualBox is a general-purpose full virtualizer for x86 hardware, targeted at server, desktop and embedded use.
How to install Vurtualbox in Linux Distro’s.
 
On Ubuntu distro:
1. To install Oracle VirtualBox 4.3.18 in Ubuntu  open a Terminal (ctrl+alt+t, Add one of the following lines according to your distribution to your /etc/apt/sources.list:

 
deb http://download.virtualbox.org/virtualbox/debian trusty contrib
deb http://download.virtualbox.org/virtualbox/debian saucy contrib
deb http://download.virtualbox.org/virtualbox/debian raring contrib
deb http://download.virtualbox.org/virtualbox/debian quantal contrib
deb http://download.virtualbox.org/virtualbox/debian precise contrib
deb http://download.virtualbox.org/virtualbox/debian lucid contrib non-free
deb http://download.virtualbox.org/virtualbox/debian wheezy contrib
deb http://download.virtualbox.org/virtualbox/debian squeeze contrib non-free

2. Save and exit the file.

ctrl+o to save and ctrl+x to exit

wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc -O- | sudo apt-key add -

3. Update source list

sudo apt-get update

4. You can now instll Virtualbox

sudo apt-get install virtualbox-4.3.18

5. Requirements: Install dkms to ensure that the virtualbox host kernel modules are properly updated, if you upgrade your linux kernel version.

sudo apt-get install dkms

and where done enjoy…