See RT-11839 for code sample.

If you open a website, for example http://www.w3schools.com/html/tryit.asp?filename=tryhtml_select3, with a HTML dropdown and click the dropdown to see the full list, the following exception is thrown, and the list is not shown:

java.lang.ClassCastException: com.sun.javafx.tk.glass.EmbeddedStage cannot be cast to com.sun.javafx.tk.glass.WindowStage
at com.sun.javafx.tk.glass.PopupStage.<init>(PopupStage.java:44)
at com.sun.javafx.tk.glass.GlassToolkit.createTKPopupStage(GlassToolkit.java:270)
at com.sun.javafx.stage.PopupWindow.storeVisible(PopupWindow.java:42)
at javafx.stage.Window.setVisible(Window.java)
at com.sun.javafx.stage.Popup.storeVisible(Popup.java:99)
at com.sun.javafx.stage.Popup.setVisible(Popup.java)
at com.sun.javafx.stage.Popup.show(Popup.java:156)
at com.sun.javafx.stage.Popup.show(Popup.java:167)
at com.sun.javafx.scene.control.skin.PopupControlSkin.showPopup(PopupControlSkin.java:122)
at com.sun.javafx.scene.control.skin.PopupControlSkin.showHidePopup(PopupControlSkin.java:79)
at com.sun.javafx.scene.control.skin.PopupControlSkin.setShowing(PopupControlSkin.java:73)
at com.sun.javafx.scene.control.skin.PopupMenuSkin.handleControlPropertyChanged(PopupMenuSkin.java:92)
at com.sun.javafx.scene.control.skin.PopupMenuSkin$1.handle(PopupMenuSkin.java:46)
at com.sun.javafx.beans.PropertySupport.fireChangedEvent(PropertySupport.java:146)
at com.javafx.preview.control.PopupMenu.setShowing(PopupMenu.java)
at com.javafx.preview.control.PopupMenu.doShow(PopupMenu.java:251)
at com.javafx.preview.control.PopupMenu.show(PopupMenu.java:244)
at com.sun.webpane.sg.theme.PopupMenuImpl$5.run(PopupMenuImpl.java:118)
at com.sun.webpane.sg.prism.InvokerImpl.invokeOnEventThread(InvokerImpl.java:26)
at com.sun.webpane.sg.theme.PopupMenuImpl.doShow(PopupMenuImpl.java:115)
at com.sun.webpane.sg.theme.PopupMenuImpl.show(PopupMenuImpl.java:62)
at com.sun.webpane.platform.PopupMenu.fwkShow(PopupMenu.java:36)
at com.sun.webpane.platform.WebPage.twkProcessMouseEvent(Native Method)
at com.sun.webpane.platform.WebPage.dispatchMouseEvent(WebPage.java:675)
at javafx.scene.web.WebView.processMouseEvent(WebView.java:366)
at javafx.scene.web.WebView.access$100(WebView.java:41)
at javafx.scene.web.WebView$2.handle(WebView.java:396)
at javafx.scene.web.WebView$2.handle(WebView.java:394)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:55)
at com.sun.javafx.event.DefaultEventDispatcher.dispatchBubblingEvent(DefaultEventDispatcher.java:173)
at com.sun.javafx.event.DefaultEventDispatcher.dispatchBubblingEvent(DefaultEventDispatcher.java:157)
at com.sun.javafx.event.DefaultEventDispatcher.dispatchEvent(DefaultEventDispatcher.java:120)
at javafx.scene.Node$7.dispatchEvent(Node.java:3863)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventRedirector.dispatchEvent(EventRedirector.java:79)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at javafx.event.Event.fireEventImpl(Event.java:172)
at javafx.event.Event.fireEvent(Event.java:162)
at javafx.scene.Node.fireEvent(Node.java:3968)
at javafx.scene.Scene$MouseHandler.process(Scene.java:1912)
at javafx.scene.Scene$MouseHandler.process(Scene.java:1753)
at javafx.scene.Scene$MouseHandler.access$600(Scene.java:1725)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:882)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:1380)
at com.sun.javafx.tk.glass.EmbeddedScene$4.run(EmbeddedScene.java:239)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:14)
at com.sun.glass.ui.win.WinApplication$1.run(WinApplication.java:33)
at java.lang.Thread.run(Thread.java:662)