Latest is from October 2016 and is:
System=75.14.93
XE-DMO=1.222.192
IOT=41.1.0
It can be obtained here
European with Postscript option
European without Postscript option
Do Not Install the wrong one. If you are in Europe and install the North American, you will without a doubt break the printer.
If you install the Postscript Europe one thinking "Hey, lets get that option for free" you won't, but you will again, break the thing. Postscript isn't just software, it is hardware. Unbreaking it won't be fast or cheap.
Xerox WorkCentre 7428 software version is currently 1.182.18 and I'm wondering if there is a newer version for that machine that will bring the software more in line with the other Xerox machines we are running. I checked on the drivers and downloads page for that machine on xerox.com but I don't see any software updates listed at all.