Index: core/units/helpers/user_helper.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/units/helpers/user_helper.php	(revision 15775)
+++ core/units/helpers/user_helper.php	(revision )
@@ -480,14 +480,36 @@
 			unset($vars['login'], $vars['logout']);
 
 			// merge back url params, because they were ignored if this was "external:" url
-			$vars['pass'] = implode(',', $vars['pass']);
-			$vars = array_merge($vars, $this->event->getRedirectParams());
+			$vars = array_merge($vars, $this->getRedirectParams($vars['pass'], 'pass'));
 
 			$template = $vars['t'];
 			unset($vars['is_virtual'], $vars['t']);
 
 			$this->event->redirect = $template;
 			$this->event->setRedirectParams($vars, false);
+		}
+
+		/**
+		 * Returns current event redirect params with given $prefixes injected into 'pass'.
+		 *
+		 * @param array  $prefixes   List of prefixes to inject.
+		 * @param string $pass_name Name of array key in redirect params, containing comma-separated prefixes list.
+		 *
+		 * @return string
+		 * @access protected
+		 */
+		protected function getRedirectParams($prefixes, $pass_name = 'passed')
+		{
+			$redirect_params = $this->event->getRedirectParams();
+
+			if ( isset($redirect_params[$pass_name]) ) {
+				$redirect_prefixes = explode(',', $redirect_params[$pass_name]);
+				$prefixes = array_unique(array_merge($prefixes, $redirect_prefixes));
+			}
+
+			$redirect_params[$pass_name] = implode(',', $prefixes);
+
+			return $redirect_params;
 		}
 
 		/**