On twitter, it was said that affected subnets are:
52.58.0.0/15
18.196.0.0/15
18.194.0.0/15
35.156.0.0/14
src: https://twitter.com/CatVsHumanity/status/985914182959759360/...
Just in case the original website goes down, here's a screenshot:
https://img2.picload.org/image/dogacarr/selection_120.jpg