I have noticed a rather strange thing with my S21 Ultra. Whenever I play a YouTube video or any kind of video from a website, I pull down the main panel screen and it shows this(See below). It automatically starts playing. What does this mean and is my phone's activity being cast on some random device? I actually have never authorized or heard of this device before. I'm no expert but I actually never cast my phone anywhere, I just use my phone for texting and calling. I'm worried that someone is hacked my phone but I have all updates for my apps and am very discipline with updating.