Fix PageCache: async rendering of blocks can corrupt layout cache #8554

Author: adrian-martinez-interactiv4

app/code/Magento/PageCache/Controller/Block.php

@@ -27,6 +27,11 @@ abstract class Block extends \Magento\Framework\App\Action\Action
      */
     private $base64jsonSerializer;
 
+    /**
+     * @var string
+     */
+    private $additionalPageCacheHandle = 'additional_page_cache_handle';
+
     /**
      * @param \Magento\Framework\App\Action\Context $context
      * @param \Magento\Framework\Translate\InlineInterface $translateInline
@@ -63,6 +68,8 @@ protected function _getBlocks()
         $blocks = $this->jsonSerializer->unserialize($blocks);
         $handles = $this->base64jsonSerializer->unserialize($handles);
 
+        $handles[] = $this->additionalPageCacheHandle;
+
         $this->_view->loadLayout($handles, true, true, false);
         $data = [];