Fix newsletter subscriptions between stores

Include store_id in query result in order to ensure that the action (subscribe/unsubscribe) it’s done in the correct store.

Author: sbaixauli

app/code/Magento/Newsletter/Model/ResourceModel/Subscriber.php

@@ -118,17 +118,37 @@ public function loadByEmail($subscriberEmail)
      */
     public function loadByCustomerData(\Magento\Customer\Api\Data\CustomerInterface $customer)
     {
-        $select = $this->connection->select()->from($this->getMainTable())->where('customer_id=:customer_id');
-
-        $result = $this->connection->fetchRow($select, ['customer_id' => $customer->getId()]);
+        $select = $this->connection
+            ->select()
+            ->from($this->getMainTable())
+            ->where('customer_id=:customer_id and store_id=:store_id');
+
+        $result = $this->connection
+            ->fetchRow(
+                $select,
+                [
+                    'customer_id' => $customer->getId(),
+                    'store_id' => $customer->getStoreId()
+                ]
+            );
 
         if ($result) {
             return $result;
         }
 
-        $select = $this->connection->select()->from($this->getMainTable())->where('subscriber_email=:subscriber_email');
-
-        $result = $this->connection->fetchRow($select, ['subscriber_email' => $customer->getEmail()]);
+        $select = $this->connection
+            ->select()
+            ->from($this->getMainTable())
+            ->where('subscriber_email=:subscriber_email and store_id=:store_id');
+
+        $result = $this->connection
+            ->fetchRow(
+                $select,
+                [
+                    'subscriber_email' => $customer->getEmail(),
+                    'store_id' => $customer->getStoreId()
+                ]
+            );
 
         if ($result) {
             return $result;