Do you remember the so called HijackClick 3 series of Internet Explorer vulnerabilities? In summary, you can force a drag and drop event simply when the user clicking a something by moving the window when the OnMouseDown event fires.
MS seems to patch these vulnerabilities some times ago (ok, I think it's really discutible this fact: disable some functions from being called when the mouse button is down for me is not a real patch, but only a temporary solution).
What's new? As you can see on a new post on SecurityFocus, MS has patched MSHTML.DLL and IEXPLORE.EXE but they have forgotten to patch the Popup.Show() function. Now an exploiter can show a popup on loading of the main window, move it and show a favorites list on the MouseDown event, and set a timer to hide the favorites list and taunt the victim who just got tricked into adding a link of our choice to their favorites list.
Also a real example of these exploit is available, just click HERE.
I think this is a clear sign that IE staff must improved, they must start thinking on something better. Patching a problem is not equals to simply disable functions, but the problem must be understood and correct.