VirtualBox test builds
Sometimes Oracle staff provide test builds of VirtualBox to users who are interested in helping to track down a particular problem. These are generally in the form of web links that expire after a week or so. Test builds can come from either the current development code or be a pre-release of a stable version of VirtualBox.
While every effort is made to ensure that the test builds are as stable as possible, test builds from the development tree will usually have issues that stable releases do not, and unless you are adventurous, we strongly advise against using them for anything other than the purpose they were provided for - and especially not on a production system. Don't let that put you off installing them to track down problems though!
Test builds of stable releases are less likely to contain severe problems, although this can still not be ruled out as they have not yet undergone pre-release testing, and we still advise against using them on production systems. However, if you do happen to find a problem in such a test build which did not occur in the last stable release, please let us know about it.
Installing Linux test builds
Test builds for Linux hosts are generally packed up in a shell script installer with the extension ".run". To install them, you first need to remove your existing VirtualBox installation (but not your virtual machines - they will continue to work with the test build) and then execute the installer. To remove the test build again, execute the installer with the parameter "uninstall" on the command line.