Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 5235)
+++ /CKEditor/trunk/CHANGES.html	(revision 5236)
@@ -64,4 +64,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/4555">#4555</a> : Non-released memory when editor is created and destroyed.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/5118">#5118</a> : Arrow keys navigation in RTL languages is incorrect.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/4721">#4721</a> : Remove attribute 'value' of checkbox in IE.</li>
 	</ul>
 	<h3>
Index: /CKEditor/trunk/_source/plugins/forms/dialogs/checkbox.js
===================================================================
--- /CKEditor/trunk/_source/plugins/forms/dialogs/checkbox.js	(revision 5235)
+++ /CKEditor/trunk/_source/plugins/forms/dialogs/checkbox.js	(revision 5236)
@@ -92,5 +92,17 @@
 								element.setAttribute( 'value', value );
 							else
-								element.removeAttribute( 'value' );
+							{
+								if ( CKEDITOR.env.ie ) 
+								{ 
+									// Remove attribute 'value' of checkbox #4721. 
+									var checkbox = new CKEDITOR.dom.element( 'input' ); 
+									element.copyAttributes( checkbox, { value: 1 } ); 
+									checkbox.replace( element ); 
+									editor.getSelection().selectElement( checkbox ); 
+									data.element = checkbox;      
+								} 
+								else 
+									element.removeAttribute( 'value' );
+							}
 						}
 					},