Microsoft released Exchange Server 2013 Cumulative Update 8 (CU8) yesterday. See KB 3030080: Cumulative Update 8 for Exchange Server 2013 for more details, including a list of fixes included in CU8.
Symantec has documented an issue with Symantec Enterprise Vault™, Symantec’s on-premises archiving solution, and Exchange 2013 CU6 and CU7. The corresponding Microsoft KBA Symantec refers to is KB 3011579. Exchange 2013 CU8 includes a fix for KB 3011579.
When planning to upgrade to Exchange 2013 CU8, customers using Symantec Enterprise Vault should check with Symantec regarding Enterprise Vault compatibility.