Microsoft released the quarterly servicing update to Exchange Server 2013. There is only one new feature: improvements in the OAB management for distributed environments.
You can read the full blog post at the Exchange Team Blog.
A great fix is KB2924519 which repairs the CU2 Installation issue when Exchange was installed on another drive than C (for example D), then the empty D:\TransportRoles\Logs\SyncHealth\Hub was created.
Also there are some changes to the Hybrid Configuration Wizard as well. You can check out the article from Michael van Horenbeeck at the ENow blog.
The complete list of reported issues is available at the Microsoft support site.