I'm running EE 2.7.2, Wygwam 3.2.2. Drag and drop image into the field doesn't work. After saving my entry and opening the page, I can view source and see the following:
<img alt="" src="data:<;base64,/9j/4R5uRXhpZgAASUkqAAgAAAAPAAABAwABAAAAQAYAAAE... .... ....</div>
If I insert an image by using the toolbar button and uploading an image, it works fine.
Update This is a bug to be addressed by P&T.