The nasty thing was that no "getting into corporate network and scanning" was required. All you had to manage was to get some browser to send a maliciously crafted request to a vulnerable app. It's easy to just have a snippet of javascript code that just posts to localhost:3000 in the hope of hitting an app. Embed that snippet on a forum that lots of rails developers visit - instant pwnage. It's spray and pray, granted, but as long as you're not trying to hit a specific target that should give you plenty of root shells on developer machines.