gistfile1.txt

diff --git a/src/Plugin/Field/FieldFormatter/EmbederatorFormatter.php b/src/Plugin/Field/FieldFormatter/EmbederatorFormatter.php
index 305e71b..1bebf84 100644
--- a/src/Plugin/Field/FieldFormatter/EmbederatorFormatter.php
+++ b/src/Plugin/Field/FieldFormatter/EmbederatorFormatter.php
@@ -5,6 +5,7 @@ namespace Drupal\embederator\Plugin\Field\FieldFormatter;
 use Drupal\Core\Field\FormatterBase;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Compnonent\Utility\Html;
 
 /**
  * Plugin implementation of the default embederator (token replacing) formatter.
@@ -41,6 +42,7 @@ class EmbederatorFormatter extends FormatterBase {
         try {
           $response = $client->request('GET', $url);
           $markup = (string) $response->getBody();
+          $markup = $this->uniquify($markup);
         }
         catch (Exception $e) {
           $markup = '<p>Unable to load ' . $url . '</p>';
@@ -58,6 +60,7 @@ class EmbederatorFormatter extends FormatterBase {
       $elements = [];
       foreach ($items as $delta => $item) {
         $markup = $token->replace($embed_pattern_field['value'], ['embederator' => $entity]);
+        $markup = $this->uniquify($markup);
         $elements[$delta] = [
           '#type' => 'processed_text',
           '#text' => $markup,
@@ -80,4 +83,23 @@ class EmbederatorFormatter extends FormatterBase {
             && ($field_definition->getName() == 'embed_id'));
   }
 
+  /**
+   * Add a random suffix to ID attributes in DOM markup.
+   *
+   * See e.g., https://api.drupal.org/api/drupal/core%21modules%21filter%21src%21Plugin%21Filter%21FilterHtml.php/function/FilterHtml%3A%3AfilterAttributes/8.2.x.
+   */
+  protected function uniquify($html) {
+    $suffix = uniqid();
+    $html_dom = Html::load($html);
+    $xpath = new \DOMXPath($html_dom);
+    foreach ($xpath
+      ->query('//[id]') as $element) {
+      $id = $element->getAttribute('id');
+      $id .= "-" . $suffix;
+      $element->setAttribute('id', $id);
+    }
+    $html = Html::serialize($html_dom);
+    return trim($html);
+  }
+
 }