Index: branches/5.2.x/core/units/helpers/user_helper.php
===================================================================
diff -u -N -r16748 -r16774
--- branches/5.2.x/core/units/helpers/user_helper.php	(.../user_helper.php)	(revision 16748)
+++ branches/5.2.x/core/units/helpers/user_helper.php	(.../user_helper.php)	(revision 16774)
@@ -1,6 +1,6 @@
 <?php
 /**
-* @version	$Id: user_helper.php 16748 2022-11-09 15:41:07Z alex $
+* @version	$Id: user_helper.php 16774 2023-11-22 08:51:16Z alex $
 * @package	In-Portal
 * @copyright	Copyright (C) 1997 - 2009 Intechnic. All rights reserved.
 * @license      GNU/GPL
@@ -722,4 +722,32 @@
 
 			return $object->Update() ? '' : 'restore_impossible';
 		}
+
+		/**
+		 * Returns user's primary group.
+		 *
+		 * @param integer $user_id User ID.
+		 *
+		 * @return integer
+		 */
+		public function getPrimaryGroup($user_id)
+		{
+			if ( $user_id <= 0 ) {
+				return $this->Application->ConfigValue('User_LoggedInGroup');
+			}
+
+			$cache_key = 'user' . $user_id . '_primary_group[%UIDSerial:' . $user_id . '%]';
+			$cache_value = $this->Application->getCache($cache_key);
+
+			if ( $cache_value === false ) {
+				$sql = 'SELECT PrimaryGroupId
+						FROM ' . TABLE_PREFIX . 'Users
+						WHERE PortalUserId = ' . $user_id;
+				$cache_value = $this->Conn->GetOne($sql);
+				$this->Application->setCache($cache_key, $cache_value);
+			}
+
+			return $cache_value;
+		}
+
 	}
Index: branches/5.2.x/core/units/users/users_event_handler.php
===================================================================
diff -u -N -r16692 -r16774
--- branches/5.2.x/core/units/users/users_event_handler.php	(.../users_event_handler.php)	(revision 16692)
+++ branches/5.2.x/core/units/users/users_event_handler.php	(.../users_event_handler.php)	(revision 16774)
@@ -1,6 +1,6 @@
 <?php
 /**
-* @version	$Id: users_event_handler.php 16692 2021-08-31 09:24:09Z alex $
+* @version	$Id: users_event_handler.php 16774 2023-11-22 08:51:16Z alex $
 * @package	In-Portal
 * @copyright	Copyright (C) 1997 - 2009 Intechnic. All rights reserved.
 * @license      GNU/GPL
@@ -1665,6 +1665,12 @@
 					WHERE PortalUserId IN (' . implode(',', $user_ids) . ')';
 			$this->Conn->Query($sql);
 
+			foreach ( $user_ids as $user_id ) {
+				$this->Application->incrementCacheSerial('u', $user_id);
+			}
+
+			$this->Application->incrementCacheSerial('u');
+
 			$sql = 'SELECT PortalUserId
 					FROM ' . $table_name . '
 					WHERE (GroupId = ' . $primary_group_id . ') AND (PortalUserId IN (' . implode(',', $user_ids) . '))';