GET method is not allowed

The usual OAuth authentification (where you can directly fill in your client ID and secret ID after clicking on the GET function of an API) does not seems to work since this night. Which implies API users have to provide their own access token… which isn’t always simple (specially for noobs such as me) with POST request (instead of GET). And those who used the GUI (which has only GET buttons) to get blocked.

I’m trying to get the match history legacy API in particular, but apparently the problem is general.

cf. Source thread.