So.. apparently this SQL injectable website does not allow user
or users
keyword.
But.. id=user
and id=users
are allowed. I have no time to determine what WAF rules are applied. All I know is that I don't really know when they will drop a request. I just try something and see if it works.
And then suddenly after randomly mashing my keys to find a working payload, this worked:
'+/*!40000union*/select+/*randomlongstringhehehehehe*/user,password+from/*anotherlongstringhehehehehe*/users%23