Seems like Intel released an updated microcode data file just within the last hour or so (when I looked at the download page the last time, it still had the 20171117 version, now it is at 20180108): https://downloadcenter.intel.com/download/27431/Linux-Processor-Microcode-Data-File
The download page also has a list of supported processors.
(Now I just have to look up how to feed that to iucode-tool...)
@ckeen There's a "releasenote" file in there with instructions, doesn't even need the iucode-tool
The package doesn't seem to contain anything new for the CPU in my notebook though (just newer than before):
microcode: CPU0 sig=0x20655, pf=0x10, revision=0x2
microcode: CPU0 updated to revision 0x4, date = 2013-06-28