Dell has rolled-out BIOS update version 1.3.4 for their popular XPS 15 9560-series notebooks. The BIOS update fixes include the recently discovered microcode bug with Intel's Skylake and Kaby Lake architectures.
https://www.notebookcheck.net/XPS-15-9560-gets-BIOS-update-fixing-Skylake-Kaby-Lake-microcode-bug.232054.0.html
so,that's all your guess?they may update the microcode to fix other bugs,and the "urgent" is for the security issues.