As you may have seen Microsoft released its Exchange Server 2013 Cumulative Update 6 quickly followed by two patches due to issues raised by customers
- Exchange Server 2013 databases unexpectedly fail over in a co-existence environment with Exchange Server 2007 (KB2997209)
- Exchange Online mailboxes cannot be managed by using EAC after you deploy Exchange Server 2013 CU6 (KB2997355)
As the hotfixes are now available I would strongly recommend installing them taking all the necessary precautions i.e. backups etc.
Updates also came out for Exchange 2010 and Exchange 2007, download these using the links below:-