On September 15th Microsoft has released Exchange Server 2013 CU10. Cumulative Update 10 contains the latest set of fixes and builds upon Exchange Server 2013 Cumulative Update 9. As a reminder CU releases are full Microsoft Exchange products allowing new installations.
The Cumulative Update 10 package can be used to perform a new installation of Exchange Server 2013 or to upgrade an existing Exchange Server 2013 installation to Cumulative Update 10.
You don't have to install Cumulative Update 1 or a later cumulative update for Exchange Server 2013 when you install Cumulative Update 10.
Cumulative Update 10 does not include updates to Active Directory Schema, but does include additional RBAC definitions requiring PrepareAD to be executed prior to upgrading any servers to CU10. PrepareAD will run automatically during the first server upgrade if Setup detects this is required and the logged on user has sufficient permission.