Here, you will find links to VirtualBox binaries and its source code.

VirtualBox binaries

By downloading, you agree to the terms and conditions of the respective license.

• VirtualBox platform packages. The binaries are released under the terms of the GPL version 2.
  • VirtualBox 4.1.4 for Windows hosts x86/amd64
  • VirtualBox 4.1.4 for OS X hosts x86/amd64
  • VirtualBox 4.1.4 for Linux hosts
  • VirtualBox 4.1.4 for Solaris hosts x86/amd64

• VirtualBox 4.1.4 Oracle VM VirtualBox Extension Pack All platforms
  Support for USB 2.0 devices, VirtualBox RDP and PXE boot for Intel cards. See this chapter from the User Manual for an introduction to this Extension Pack. The Extension Pack binaries are released under the VirtualBox Personal Use and Evaluation License (PUEL).
  Please install the extension pack with the same version as your installed version of VirtualBox! If you are using VirtualBox 4.0.12, please download the extension pack here.

• VirtualBox 4.1.4 Software Developer Kit (SDK) All platforms

See the changelog for what has changed.
You might want to compare the

• SHA256 checksums or the
• MD5 checksums

to verify the integrity of downloaded packages.
Note: After upgrading VirtualBox it is recommended to upgrade the guest additions as well.

Take it from virtualbox.org