The lawsuit was put in to motion by someone called Jeffrey Berk who is representing a group of Coinbase customers who bought or sold BCH between the 19th-21st December, 2017.

It seems that Coinbase is tangled in a web of litigation right now with the aforementioned lawsuit as well as a separate and more recent lawsuit which was filed on the 2nd March, 2018 where the allegation is that Coinbase has kept clients unclaimed cryptocurrencies unfairly.