When moving a file to the window containing the dropupload component on IE 11, the drop area appears.
If the drop is cancelled by moving the mouse cursor outside of the window and releasing or right clicking while holding the file, the drop area disappear.
if the file is released in the window, but out of the drop area, the drop area does not disappear.
The drop area will be displayed until the next event triggering its visibility (drop completed on the area, right clicking while holding a file over the window, bringing a file in and out of the window.)

affected version 6.5.0+ (tested until zk 8.0.0 FL 20150908)