Earlier this year, users of Chromecast streaming dongles, Google Home devices, and smart TVs were inundated with a message promoting YouTuber PewDiePie’s channel. The hijacking is said to be part of an ongoing subscriber count battle on the video sharing site. The hackers behind it reportedly took advantage of poorly configured routers that had the Universal Plug and Play (UPnP) service enabled, which caused the routers to forward public ports to the private devices and be open to the public internet.

https://blog.trendmicro.com/trendlabs-security-intelligence/upnp-enabled-connected-devices-in-home-unpatched-known-vulnerabilities/