You are here: Sysadmins of the North » Web applications » Web application security » Check WordPress Core files integrity

Check WordPress Core files integrity

Check WordPress integrity and verify WordPress Core files’ md5 checksums against WordPress’ checksums API, using this standalone PHP file. I chose to use a standalone PHP script to check the md5sum of WordPress Core files against the API so you’re not dependent on a possibly hacked WordPress installation. This kind of guarantees the result can be trusted, as opposed to using a WordPress plugin. I think this is a better integrity check of WordPress Core files.

What do you think of this approach? Let me know through the comments, thanks!

Because it is a standalone PHP script, and not part of WordPress ecosystem, you need to include wp-includes/version.php. Otherwise you are not able to use the $wp_version and $wp_locale variables that are required.

“I trust you”, do we trust the WordPress PHP files we have on our systems? Or is the integrity not checked?

Jan Reilink

Copy and paste the following code into a new file and upload the file to your WordPress root folder.

<?php
/**
 * Verify WP Core files md5 checksums, outside WordPress.
 * Use this script to verify md5 checksums of WordPress core files.
 * 
 * Follow me on Twitter: @Jan_Reilink
 * Please donate: https://www.paypal.me/jreilink
 */

if ( version_compare( PHP_VERSION, '5.6.29', '<' ) ) {
    die( 'You are using PHP Version: ' . PHP_VERSION . '.
        I think you should use a higher PHP version, at least 5.6.29!
        (change the PHP version check if you must...) ' );
}

/**
 * Put this file in the your WordPress root folder, leave ABSPATH
 * defined  as './'.
 */
define('ABSPATH', './');
if ( defined( 'ABSPATH' ) ) {
    include( ABSPATH . 'wp-includes/version.php' );
    $wp_locale = isset( $wp_local_package ) ? $wp_local_package : 'en_US';
    $apiurl = 'https://api.wordpress.org/core/checksums/1.0/?version=' . $wp_version . '&locale=' .  $wp_locale;
    $json = json_decode ( file_get_contents ( $apiurl ) );
    $checksums = $json->checksums;

    foreach( $checksums as $file => $checksum ) {
        $file_path = ABSPATH . $file;

        if ( file_exists( $file_path ) ) {
            if ( md5_file ($file_path) !== $checksum ) {
                // do something when a checksum doesn't match
                echo "HELP! Checksum for " .$file_path ." does not match!";
            }
        }
    }
}
?>Code language: PHP (php)

Now run the file in your browser. No result means everything is OK.

Searching for backdoors in PHP files

When going through a hacked WordPress searching for backdoors, there is not really an advantage in verifying core files checksums first. One might say you don’t have to scan files which checksums match, but in my opinion you just have to scan everything.

So if you found this article interesting, you may also like my post using grep to search for backdoors. The post contains a lot of useful grep examples and information, use it wisely.

Show Your Support

donate with Paypal

If you want to step in to help me cover the costs for running this website, that would be awesome. Just use this link to donate a cup of coffee ☕($10 USD or €10 EUR for example). And please share the love and help others make use of this website. Thank you very much! <3 ❤️

2 thoughts on “Check WordPress Core files integrity”

  1. oops ziet er niet goed uit vrees ik ? HELP! Checksum for ./wp-content/themes/twentyseventeen/footer.php does not match!

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top