I found a ghost Unity logo icon on my exe file ! 
What happens is, when I set my icon in the Editor and then build the app, that’s fine : the icon is attached to my exe file and I can see it correctly on the explorer. But then if I right-click and select property, the displayed icon integrates a sort of alpha layer representing the Unity logo…
For example, I attached a beautiful red butterfly on an incredible pale yellow background icon (this is for test purposes only ;)) and also the resulting visual result in the property window.
Anyone experienced and solved that ? Thanks.
