Pretty sure that is a reference to DoubleClick, which Google bought, who has a pretty long history of allowing their network to be used to distribute malware.

Pretty sure that is a reference to DoubleClick, which Google bought, who has a pretty long history of allowing their network to be used to distribute malware. The basic summary as I remember it is: Website A has a deal to show DoubleClick ads. DoubleClick can choose to directly show an ad from their network, or sell the spot to another smaller ad network. There may be multiple layers of reselling here. Someone signs up to some tiny ad network that is just happy to get customers and don't care too much about vetting. That someone probably uses a stolen CC to buy ad space, and because you can inject JavaScript as part of your ad, this person injects some malware. There was a bunch of pretty high-profile cases of this happening on major websites (NY Times and Wired, iirc). Some were done using flash, back when that was a thing.