Firing contextmenu event in Firefox AddOn gives different Elements (XPCNativeWrapper vs. XULElement)?

Executing this JavaScript:

window.addEventListener("contextmenu", function(e) { afunction(e); }, true);

function updateReflectMenu(anEvent) {
  var elemUnderMouse = anEvent.target;
  alert(elemUnderMouse);
}

within an AddOn in Firefox 3.5 gives me something like:

[object XPCNativeWr开发者_运维知识库apper [object HTMLSpanElement]]

Exactly what I'm looking for. Executed with Firefox 1.5 or 2.x I get:

[object XULElement]

Unfortunately I was unable to find any information about that! Any help is much appreciated.

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anEvent.originalTarget

https://developer.mozilla.org/en/DOM/event.originalTarget

tested with FF 1.5, 2.0 and 3.5!