https://www.ruby-lang.org/en/news/2017/09/14/ruby-2-4-2-released/
https://www.ruby-lang.org/en/news/2017/09/14/ruby-2-3-5-released/
https://www.ruby-lang.org/en/news/2017/09/14/ruby-2-2-8-released/
All released yesterday.
I tried cloning and running the update.sh script which failed on my machine, rather than shave that yak, I created this issue. I assume it's probably a quick update for whoever normally does it.