Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 5407)
+++ /CKEditor/trunk/CHANGES.html	(revision 5408)
@@ -159,4 +159,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/5121">#5121</a> : Recognizes the &lt;br /&gt; tag as a separator when apply block styles in enterMode=BR.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/5575">#5575</a> : CKEDITOR.replaceAll should consider all kind of white spaces between class names.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/5582">#5582</a> : Prevent the default behavior when click the 'x' button to close dialog box.</li>
 		<li>Updated the following language files:<ul>
 			<li><a href="http://dev.fckeditor.net/ticket/5326">#5326</a> : Catalan;</li>
Index: /CKEditor/trunk/_source/plugins/dialog/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 5407)
+++ /CKEditor/trunk/_source/plugins/dialog/plugin.js	(revision 5408)
@@ -249,4 +249,5 @@
 					if ( this.fire( 'cancel', { hide : true } ).hide !== false )
 						this.hide();
+					evt.data.preventDefault();
 				}, this );