ACP2E-4072: VAT Validation fails because of VAT API rate limiter - triggers false positive customer group change

Author: o-dubovyk

app/code/Magento/Customer/Model/Vat.php

@@ -139,22 +139,14 @@ public function getCustomerGroupIdBasedOnVatNumber($customerCountryCode, $vatVal
         ];
 
         if (isset($vatClassToGroupXmlPathMap[$vatClass])) {
-            $groupId = (int)$this->scopeConfig->getValue(
+            $groupId = $this->scopeConfig->getValue(
                 $vatClassToGroupXmlPathMap[$vatClass],
                 ScopeInterface::SCOPE_STORE,
                 $store
             );
-
-            if (!$groupId) {
-                $groupId = (int)$this->scopeConfig->getValue(
-                    GroupManagement::XML_PATH_DEFAULT_ID,
-                    ScopeInterface::SCOPE_STORE,
-                    $store
-                );
-            }
         }
 
-        return $groupId;
+        return $groupId ? (int)$groupId : null;
     }
 
     /**

app/code/Magento/Customer/Observer/AfterAddressSaveObserver.php

@@ -159,7 +159,10 @@ public function execute(Observer $observer)
                     $customer->getStore()
                 );
 
-                if (!$customer->getDisableAutoGroupChange() && $customer->getGroupId() != $newGroupId) {
+                if (!$customer->getDisableAutoGroupChange() &&
+                    $newGroupId !== null &&
+                    $customer->getGroupId() != $newGroupId
+                ) {
                     $customer->setGroupId($newGroupId);
                     $customer->save();
                     $this->customerSession->setCustomerGroupId($newGroupId);