Issue #3264239: A PCRE error (#2) occurred during results highlighting.

src/Plugin/search_api/processor/Highlight.php

@@ -4,6 +4,7 @@ namespace Drupal\search_api\Plugin\search_api\processor;
 
 use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\Unicode;
+use Drupal\Component\Utility\Xss;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginFormInterface;
 use Drupal\Core\Render\Element;
@@ -656,7 +657,8 @@ class Highlight extends ProcessorPluginBase implements PluginFormInterface {
    */
   protected function highlightField($text, array $keys, $html = TRUE) {
     if ($html) {
-      $texts = preg_split('#((?:</?[[:alpha:]](?:[^>"\']*|"[^"]*"|\'[^\']\')*>)+)#i', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
+      $filtered_text = Xss::filter($text);
+      $texts = preg_split('#((?:</?[[:alpha:]](?:[^>"\']*|"[^"]*"|\'[^\']\')*>)+)#i', $filtered_text, -1, PREG_SPLIT_DELIM_CAPTURE);
       if ($texts === FALSE) {
         $args = [
           '%error_num' => preg_last_error(),