I was sure I had seen an example of someone revealing this several years ago, but I can't find the article again, so it's probably misinformation. I'm sorry for repeating it.
There are definitely "spy" TVs modified by state security groups that do this, but that's not what I was claiming.
I believed this for a time, but now I believe it is an urban legend. Granted a plausible one, and one that might be true in the future... but not true as of yet.