A group of researchers from Columbia University have published the results of some experiments with mixed mode digital TV broadcasts here.
The problem is that the new but widely implemented HbbTV standard allows HTML to be embedded in with the picture data. What could possibly go wrong?
Well apart from the fact you only need an encoder and transmitter to mess up all the sets in range by sending them HTML spam, the Columbians reckon that with the right HTML you can turn people’s tellies into a botnet and attack targets through their internet connection. I’m not yet convinced this will work in practice, but building a web browser in to anything has always been risky when it implements more than plain HTM. It’s always been possible to broadcast alternative TV and radio signals over the top of legitimate channels, but generally, it doesn’t happen in practice.