VirtualBox 4.3.14 has been released, here's how you can install it in Fedora 20. This release mostly focuses on maintenance, you can view a complete list of changes in the VirtualBox 4.3.14 changelog.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each:
sudo wget http://download.virtualbox.org/virtualbox/rpm/fedora/virtualbox.repo
sudo yum update
sudo yum install virtualbox-4.3
sudo yum install virtualbox-dkms
Source: Linux G
Additional resources for VirtualBox
Additional Fedora Resources