An old, beat-up oven with a warped door may indeed let enough microwaves out through the cracks to be a hazard, but there is extremely little leakage from today’s carefully designed ovens.
Moreover, the instant the door is opened, the magnetron shuts off and the microwaves disappear like the light when you turn off a lamp.
What about the glass door itself?
Microwaves can penetrate glass but not metal, so the glass door is covered with a perforated metal panel that lets light come through so you can see inside, but that the microwaves can’t get through because their wavelength (4¾ inches) is simply too big to fit through the holes in the metal panel.
There is no basis for the belief that it is hazardous to stand closer than several feet from an operating microwave oven.
