Similar to what happened with Update Rollup 4, this one was released a few weeks ago but was almost immediately withdrawn due to a bug that affected DAGs...
Now version 2 has been released. For a full description of this RU, please check KB2785908 and to download it click here.
As with every RU or SP, Microsoft has updated the useful Exchange Server and Update Rollups Build Numbers wiki page.
I haven’t applied it on my lab yet, but will let you know as soon as I do.