amp-wordfence-compat.php

<?php
/**
 * AMP Wordfence Compat plugin bootstrap.
 *
 * @package   Google\AMP_Wordfence_Compat
 * @author    Weston Ruter, Google
 * @license   GPL-2.0-or-later
 * @copyright 2020 Google Inc.
 *
 * @wordpress-plugin
 * Plugin Name: AMP Wordfence Compat
 * Plugin URI:  https://gist.github.com/westonruter/3bad77db53496c7103dd64ca1a0e1cf1
 * Description: Compatibility plugin to prevent Wordfence from causing AMP validation errors. In particular, this ensures the Ajax watcher logic is included in AMP Dev Mode.
 * Version:     0.2
 * Author:      Weston Ruter, Google
 * Author URI:  https://weston.ruter.net/
 * License:     GNU General Public License v2 (or later)
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 */

namespace Google\AMP_Wordfence_Compat;

add_filter(
	'amp_dev_mode_element_xpaths',
	function ( $xpaths ) {
		// @todo The following can be revised once ampdevmode flags can be added to enqueued scripts and styles. See <https://github.com/ampproject/amp-wp/issues/4598>.
		$xpaths[] = '//script[ contains( text(), "var WFAJAXWatcherVars" ) ]';
		$xpaths[] = '//script[ contains( @src, "wp-includes/js/jquery/jquery.js" ) ]';
		$xpaths[] = '//script[ contains( @src, "wp-includes/js/jquery/jquery.min.js" ) ]'; // As of WordPress 5.6.
		$xpaths[] = '//script[ contains( @src, "wp-includes/js/jquery/jquery-migrate.js" ) ]';
		$xpaths[] = '//script[ contains( @src, "wp-includes/js/jquery/jquery-migrate.min.js" ) ]';
		$xpaths[] = '//script[ contains( @src, "wordfence/js/admin.ajaxWatcher." ) ]';
		$xpaths[] = '//link[ contains( @href, "wordfence/css/wordfenceBox." ) ]';

		// Props @titopu per https://gist.github.com/westonruter/3bad77db53496c7103dd64ca1a0e1cf1?permalink_comment_id=5139391#gistcomment-5139391
		$xpaths[] = '//script[ contains( text(), "var WordfenceI18nStrings" ) ]';
		$xpaths[] = '//script[ contains( @src, "wordfence/js/wfi18n." ) ]';
		return $xpaths;
	}
);

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c

@westonruter Hello. I was directed to your mini plugin by WordFence after asking WordFence for help with a validation error that the official Google AMP plugin is flagging. The plugin (WordFence Compatibility) did not resolve the error. I can provide the raw validation data to you directly, if helpful. I have asked WordFence on the chain linked above to continue to look into the issue, and would appreciate your help, too. Thank you.

@Marguerite-star Please open a topic on our support forum: https://wordpress.org/support/plugin/amp/

I added two new lines to the file, and now it works for me. I'm not sure if it's safe, but the AMP error has been resolved.

$xpaths[] = '//script[ contains( text(), "var WordfenceI18nStrings" ) ]';
$xpaths[] = '//script[ contains( @src, "wordfence/js/wfi18n." ) ]';

@titopu Thanks. Those changes look good. I'll add those to my Gist.