We have recently uncovered an issue that affects this Service Pack 1 package and that may prevent customers who have Service Pack 1 from deploying future public or cumulative updates. Therefore, we have deactivated this update. A new update is released to resolve the issue and can be found at KB 2880552.
Microsoft SharePoint Server 2013 Service Pack 1 (SP1) provides the latest updates for SharePoint Server 2013. This service pack includes two kinds of fixes:
Previously unreleased fixes that are included in this service pack. In addition to general product fixes, these fixes include improvements in stability, performance, and security.
All the monthly security updates that were released through January 2014, and all the Cumulative Updates that were released through December 2013.