Reddit users thevincentasteroid and MMD3_ posted about an auto-playing video ad (with sound) on the home screen. The ad is for Chicken Tender Wraps from Carl’s Jr. When it begins auto-playing, it pushes all the other UI elements out of focus and goes almost full-screen, returning to the home screen after it has played through once.
I’m still on an early gen Chromecast and never see any adverts. Very occasionally crashes (once a fortnight).