In this last batch of Lync Cumulative Updates, two of them (1, 2) have no description of what is fixed, what is added, or any information about them whatsoever.
So I asked my Microsoft contact what exactly these updates are supposed to do?
From the product group I found out that there were some code updates done which improves the performance and some updates that not visible outside. I would recommend installing them in your environment.
So there you go. It would be nice if Microsoft threw in a line basically saying the above.