Exchange 2013 Cumulative Update 13 contains approximately 21 fixes along with new daylight saving time (DST) update for Exchange. One notable security issue that is patched in this version of Exchange is described in MS16-079. For new installations of Exchange 2013 you should install Exchange 2013 using the latest downloadable Exch CU media. Any existing version of Exchange 2013 can be upgraded directly to Exchange 2013 CU13. **Warning: Exchange 2013 CU13 introduces a public folder indexing issue**. For this reason we recommend skipping CU13 and instead installing CU15 or later as CU14 also contains the public folder indexing bug.