I caught it in time - and thankfully Disney has the 2-step process (you have to confirm the change or cancellation) when changing/cancelling FP+ - but beware, because the cancel and modify buttons are on opposite sides between the app and the website!!!
On the app Cancel is on the left and Modify is on the right, so when I was looking online I automatically clicked that and then saw the screen “Are you sure you want to cancel?” (or however they phrase it)!! Immediately clicked out of there and looked. On the website, Modify is on the left and Cancel is on the right!!
I know Disney IT is the source of many jokes and much frustration, but that one they brought on themselves!! Consistency people!! Keep things on the same side of the screens!!!