Added subscription limit in order to avoid mass subscriptions

lib/Models/Subscriber.php

@@ -14,6 +14,8 @@ class Subscriber extends Model {
   const STATUS_UNSUBSCRIBED = 'unsubscribed';
   const STATUS_UNCONFIRMED = 'unconfirmed';
 
+  const SUBSCRIPTION_LIMIT_COOLDOWN = 60;
+
   function __construct() {
     parent::__construct();
 
@@ -158,9 +160,27 @@ class Subscriber extends Model {
       'signup_confirmation.enabled'
     );
 
+    // set user ip
+    $subscriber_data['ip'] = (isset($_SERVER['REMOTE_ADDR']))
+      ? $_SERVER['REMOTE_ADDR']
+      : null;
+
+    // make sure we don't allow too many subscriptions with the same ip address
+    $subscription_count = Subscriber::where('ip', $subscriber_data['ip'])
+      ->whereRaw(
+        'TIME_TO_SEC(TIMEDIFF(NOW(), created_at)) < ?',
+        self::SUBSCRIPTION_LIMIT_COOLDOWN
+      )
+      ->count();
+
+    if($subscription_count > 0) {
+      throw new \Exception(__('You need to wait before subscribing again.', 'mailpoet'));
+    }
+
     $subscriber = self::findOne($subscriber_data['email']);
 
     if($subscriber === false) {
+
       // create new subscriber
       $subscriber = self::createOrUpdate($subscriber_data);
       if($subscriber->getErrors() !== false) {