OWA showing blank page in Exchange 2010

After certain rollups or patches are applied to Exchange 2010 OWA may start showing a blank page instead of the login page and the URL will look something like https://myexchange.com/owa/auth/logon.aspx?url=https://myexchange.com/owa/&reason=0

To fix this issue open Exchange management console go to your Exchange installation bin folder, typically this is C:\Program Files\Microsoft\Exchange Server\V14\Bin and run updatecas.ps1