Weird pink magenta border flashing around elements

For whatever reason when on the front page of YouTube, this magenta border will flash on and off around the top header as well as the button elements, I have no idea if this is Firefox or yt, but I've tried everything, on YouTube, I've tried fixing it in troubleshooting, code, accessibility, restarting browser and computer, randomly removing extensions. Nothing is stopping it. It briefly tried doing it on a different site but stopped on it's own, it's only effecting YouTube and Firefox