You want to paste in a message body some picture but it is often a way too big and you wish to resize it. However, when you drag a corner resize point, you can easily squeeze original proportion of the picture.
Engineering made a fix which is available in gw18.2.1-136069 client build onward. The fix is to hold down a Shift key while resizing the window. This will bring back or keep original picture proportion while resizing the picture.