I didn't personally do this one, but I once worked at a job where I was tasked with updating a kickstart file from RHEL6 to 7. I don't remember the details, but in the postscript, there was a variable that was set in 6 but not 7. That variable was then used in a command like rm -rf /${variable}.

It took me a little while to figure out why every system imaged with that kickstart was emptying its own filesystem.