https://arstechnica.com/tech-policy/2019/09/studies-google-netflix-and-others-are-watching-how-you-watch-your-tv/

Modern TV, coming to you over the Internet instead of through cable or over the air, has a modern problem: all of your Internet-connected streaming devices are watching you back and feeding your data to advertisers. Two independent sets of researchers this week released papers that measure the extent of the surveillance your TV is conducting on you. They also sort out who exactly is benefiting from the massive amounts of consumer data that is taken with or without consumer knowledge.

The first study (PDF), conducted by researchers at Princeton and the University of Chicago, looked specifically at Roku and Amazon set-top devices. A review of more than 2,000 channels across the two platforms found trackers on 69% of Roku channels and 89% of Amazon Fire TV channels.