Our original source for the upcoming Canon EF 50mm f/1.8 STM has let us know that the previously “leaked” image of the lens was definitely a fake, which is something that was figured out relatively quickly by folks on the forum.
Our source says about the physical design of the new lens:
The diameter of the lens body is the same, not variable like in the picture. The focus ring is also not as wide as in the fake picture.
We're still expecting to see this announced sometime in April, with availability coming soon after.