Validate message content and subject

main/inc/ajax/message.ajax.php

@@ -12,8 +12,15 @@ $action = $_GET['a'];
 
 switch ($action) {
     case 'send_message':
-        $subject = isset($_REQUEST['subject']) ? $_REQUEST['subject'] : null;
-        $result = MessageManager::send_message($_REQUEST['user_id'], $subject, $_REQUEST['content']);
+        $subject = isset($_REQUEST['subject']) ? trim($_REQUEST['subject']) : null;
+        $messageContent = isset($_REQUEST['content']) ? trim($_REQUEST['content']) : null;
+
+        if (empty($subject) || empty($messageContent)) {
+            echo Display::display_error_message(get_lang('ErrorSendingMessage'));
+            exit;
+        }
+
+        $result = MessageManager::send_message($_REQUEST['user_id'], $subject, $messageContent);
         if ($result) {
             echo Display::display_confirmation_message(get_lang('MessageHasBeenSent'));
         } else {