Cumulative Update 10 contains the latest set of fixes and builds upon Exchange Server 2013 Cumulative Update 9.
As per Microsoft September 2015 Quarterly Exchange Update Notes,
1.The release includes fixes for customer reported issues, minor product enhancements and previously released security bulletins, including MS15-103.
2.A complete list of customer reported issues resolved can be found in Knowledge Base Article KB3078678. Customers running any previous release of Exchange Server 2013 can move directly to Cumulative Update 10.
3. Customers deploying Exchange Server 2013 for the first time may skip previous releases and start their deployment with Cumulative Update 10 directly.
Note:
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.
To download Cumulative Update 10 for Exchange 2013, Click Here