Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 6028)
+++ /CKEditor/trunk/CHANGES.html	(revision 6029)
@@ -79,4 +79,5 @@
 		<li><a href="http://dev.ckeditor.com/ticket/6403">#6403</a> : [Opera] Font name options is not correctly marked in dropdown list.</li>
 		<li><a href="http://dev.ckeditor.com/ticket/4534">#4534</a> : [Opera] Arrow key to navigate through combo list has side effects of window scrolling.</li>
+		<li><a href="http://dev.ckeditor.com/ticket/6534">#6534</a> : [Opera] Menu key brings up both CKEditor and browser context menu.</li>
 		<li><a href="http://dev.ckeditor.com/ticket/6416">#6416</a> : [IE9] Unable to make text selection with mouse in source area.</li>
 		<li><a href="http://dev.ckeditor.com/ticket/6417">#6417</a> : [IE9] Context menu opens at the upper-left corner always.</li>
Index: /CKEditor/trunk/_source/plugins/contextmenu/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/contextmenu/plugin.js	(revision 6028)
+++ /CKEditor/trunk/_source/plugins/contextmenu/plugin.js	(revision 6029)
@@ -1,3 +1,3 @@
-/*
+/*
 Copyright (c) 2003-2010, CKSource - Frederico Knabben. All rights reserved.
 For licensing, see LICENSE.html or http://ckeditor.com/license
@@ -225,4 +225,17 @@
 				},
 				this );
+
+			if ( CKEDITOR.env.opera )
+			{
+				// 'contextmenu' event triggered by Windows menu key is unpreventable,
+				// cancel the key event itself. (#6534)  
+				element.on( 'keypress' , function ( evt )
+				{
+					var domEvent = evt.data;
+
+					if ( domEvent.$.keyCode == 0 )
+						domEvent.preventDefault();
+				});
+			}
 
 			if ( CKEDITOR.env.webkit )