Microsoft Just released CU3 for Exchange 2013. The next update should be SP1 and this will be equivalent to CU4.
CU3 includes the following enhanchments:
- Usability improvements when adding members to new and existing groups in the Exchange Administration Console
- Online RMS available for use by non-cloud based Exchange deployments
- Improved admin audit log experience
- Windows 8.1/IE11 no longer require the use of OWA Light
As always the CU is a full installation and can also be used to perform a fresh install of Exchange server.
You can grab the download from here
Please note, CU3 does not add support for windows 2012R2, that will come with SP1.