Cumulative update package 13 for SQL Server 2008 Service Pack 3 was released on September 16, 2013. You can get more information from the KB listed below.
2880350 Cumulative update package 13 for SQL Server 2008 SP3
For the issues that fix in this CU, please refer to the below table:
VSTS bug number
KB article number
FIX: Index size increases significantly after you rebuild the index online and the RCSI is enabled in SQL Server 2008 or in SQL Server 2008 R2
FIX: Nonclustered index corruption may occur when you run a complex UPDATE statement together with a NOLOCK hint against a table in SQL Server 2008
For more information on SQL CU version, please refer to the following link: