Microsoft Released CU9 for Exchange 2013 and recommend their customers to upgrade to this version as it has a lot of bug fixes in it. For more info on this release you can look here:
Note that there are 2x PowerShell scripts to download, once to put the server into maintenance mode and the other to take the server out of maintenance mode.
Exchange 2013 - CU9 Upgrade 1
To do the upgrade it is fairly easy, you run the setup (from the CU9 file you extracted) as administrator and then follow the prompts. You can let the GUI do the AD/Schema Upgrade or you can run it manually from an elevated prompt.
In this exercise i am going to list all the screen shots but they are all self explanatory.