Red spooky box of death, not sure if this is a bug but Idk wtf this is

This red box of jagged text has been appearing very frequently while I'm playing LoL, and I have no idea what this is and it honestly scares me a lot. So far I've not attempted to click anything on it except the X in the top right knowing that would probably close out of whatever this is. Also, I've never seen this box in any other game I own, and it only started appearing after the most recent patch notes.