From Steam:

"I was trying to change some of the keybindings so that I could use the extra buttons on my mouse and somehow I *disabled* the Escape key by accident and now I cannot open the menu in game anymore. The Escape key does nothing now, and none of the keys will open the menu anymore. I don't want to just Alt+F4 because I'm in the middle of a run, is there anything that I can do? 

=> Players shouldn't be able to disable the keybind that allows you to change keybinds

Note: this was fixed by using a controller, but raising it to your attention in case a player would encounter the same issue without having a controller at hand to fix it.