Edit: 7/3 added MSDN and VL ISO screenshot and explanation
It’s been a fun couple of months for guys like me that watch SharePoint patching. Earlier this month Microsoft discovered a particularly nasty bug in SharePoint 2013 Service Pack 1 and they pulled it. They locked their best and brightest patchmeisters into a room, threw in some Mt. Dew and Snickers bars and had them crank out a newer, better, stronger, more-able-to-be-patched version of Service Pack 1. If you were one of the people that installed the first, broken SP1, the fix is to install the new, shiny SP1 over top of it. The problem is figuring out which version of SP1 you have installed. The new SP1 looks an awful lot like his older brother, right down to the Farm build number (15.0.4569.1000). There is an easy way to tell them apart in Central Administration. Click the Upgrade and Migration link on the left, then Check product and patch installation status. That should take you to the /_admin/PatchStatus.aspx page. A first generation SP1 server will look like this:
The two important pieces are the KB article for the patch, KB2817429, and the patch version, 15.0.4569.1506.
A second generation SP1 server will look like this:
Its KB number is KB2880552 and it build number is 15.0.4571.1502.
If you installed SharePoint 2013 from MSDN or Volume License (VL) media it might have Service Pack 1 integrated. In that case, everything is okay. It's patch status page looks like this:
If you have the Bad SP1 just install the Good SP1 over top of it like any other update. Don’t forget to run the Config Wizard afterwards to show SharePoint you really mean business. If your server was installed with the MSDN or VL media you can still install the new SP1 over top if you want to be super sure you're up to date.
Don’t forget to follow @SP2013Patches on Twitter and bookmark my SharePoint 2013 Builds page to keep on all the patching craziness.