Er....... C4 NEws?
It was Carole Cadwalladr of the Grauniad whongo the scoop. C4N have their own scoop in about ten minutes time, having apparently carried out a traditional fake client sting on CA with secret filming, but that's a separate investigation AFAIK
https://www.theguardian.com/news/2018/mar/17/cambridge-analytica-facebook-influence-us-election