Note: Update 2 is available for Vivado 2015.4 and should, in most cases be used instead of update 1. Update 2 is cumulative and contains all of the content of update 1. Please see (Xilinx Answer 66246)
The Vivado 2015.4 tool update (2015.4.1) addresses the following issues:
Vivado 2015.4 Update 1 provides production support of the VU125 and VU065 -1 and -2 devices.
For designs leveraging these devices, Xilinx recommends installing this update.
For all other devices, please continue to use the Vivado 2015.4 release.
Downloading and installing the Vivado 2015.4 update (2015.4.1)
The update is available at: Vivado 2015.4 Update 1 Image (TAR/GZIP - 1.14GB)
MD5 SUM Value: d24fc9fdc5b91b6c9b4f2b5d45defdc
It must be applied to an existing 2015.4 installation (build 2015.4_1118_2) and will bring the Vivado version to 2015.4.1.
Additional specific fixes included in Vivado 2015.4.1
For Vivado 2015.4 known issues see: (Xilinx Answer 63538)
For known issues related to a specific IP please search the support site for "Known Issues" + the IP name.