I have this very simple ControlTemplate:

<ControlTemplate TargetType="{x:Type ContextMenu}">
                    <Border 
                           Name="Border"
                           Background="{StaticResource BlueBackground}"
                           BorderBrush="LightBlue"
                           CornerRadius="10"
                           BorderThickness="1" >
                        <StackPanel IsItemsHost="True"/>
                    </Border>
                </ControlTemplate>

I made it to create a nifty jawdroppingly beautiful rounded corner! However, when I point the mouse over a contextmenu a MouseOver Trigger fires from somewhere that draws a terribly ugly nearly square border on top of my nifty rounded border!

Where is it coming from??

EDIT: The most likely cause is that the ContextMenu is an ItemsControl that holds MenuItems, even when my ContextMenu holds a single UserControl. So the UserControl is seen as a MenuItem and highlighted when the IsMouseOver==true! What is the easiest way to disable this behaviour?