We just started experiencing the same issue. I was woken up early yesterday morning to "voices." Came downstairs to find the TV was on. I was certain I had turned it off when I went to bed, but thought my it was my imagination (afterall, I did have a bit too much wine the night before 
). Proceeded to go back to bed. Two hours later I got up and - you guessed it - the TV was on again!
When my husband returned from his trip last night I told him what happened. He mentioned that he tried to access the football game on Thursday evening using the FIOS app on his iPhone. I asked if he might have changed some sort of setting through the app but he was certain he didn't. He said I must not have turned the tv off (even though I KNEW I had - twice). Low and behold, while we sat on our porch & conversed through the evening, the TV (previously off) all of a sudden turned on about 11 pm EST! Ooooh - Casper is in the house, LOL! 👻 Needless to say, I turned the volume all the way down, then turned off the TV - let's see if it's on in the morning again. YEP - IT WAS ON!
So, on to Google to search this morning for a solution and found this thread. We have followed the suggestion to disable the CEC:
Menu>Settings>Audio & Video>Video Settings>TV Input Control>Disable
You get a pop-up box in the lower-right corner asking, "Do you want to apply this setting to other STBs in the home network?" Choose Yes, then press the OK button twice. Press the Exit button to exit the menu.
We'll see if this works in the next 24 hours and update the results here. Fingers crossed! 🤞
For information purposes, here's our equipment:
STB: Arris VMS1100 (multi-room DVR)
TV: Sony Bravia XBR-52XH909 (over 7 years old)