code: public function setAcceptedExtensions($acceptedExtensions)
      {
          // We must not allow file extensions that are globally disabled.
          $allowedDownload = StringUtil::trimsplit(',', $GLOBALS['TL_CONFIG']['allowedDownload']);
  
          if (!is_array($acceptedExtensions)) {
              $acceptedExtensions = StringUtil::trimsplit(',', $acceptedExtensions);
          }
  
          $this->acceptedExtensions = array_map('strtolower', array_intersect($allowedDownload, $acceptedExtensions));
      }
docs: Set the allowed file extensions.
  
  @param string|array $acceptedExtensions The list of accepted file extensions.
  
  @return void
  
  @SuppressWarnings(PHPMD.Superglobals)
  @SuppressWarnings(PHPMD.CamelCaseVariableName)