Index: branches/5.2.x/core/units/helpers/ajax_form_helper.php
===================================================================
diff -u -N -r15357 -r15546
--- branches/5.2.x/core/units/helpers/ajax_form_helper.php	(.../ajax_form_helper.php)	(revision 15357)
+++ branches/5.2.x/core/units/helpers/ajax_form_helper.php	(.../ajax_form_helper.php)	(revision 15546)
@@ -82,7 +82,10 @@
 			}
 			else {
 				if ( !isset($params['redirect_to']) && ($event->redirect === true || strlen($event->redirect) > 0) ) {
-					$params['redirect_to'] = $this->Application->HREF($event->redirect, '', $event->getRedirectParams(), $event->redirectScript);
+					$redirect_to = $this->Application->HREF($event->redirect, '', $event->getRedirectParams(), $event->redirectScript);
+
+					// is used from JavaScript / redirecting, so any "&" could break it
+					$params['redirect_to'] = str_replace(Array ('&', '%5C'), Array ('&', '\\'), $redirect_to);
 				}
 
 				$params = array_merge($params, $event->getRedirectParams());