Backup and Staging by WP Time Capsule < 1.21.16 - Authentication Bypass Proof Of Concept

An authentication bypass was recently discovered (https://www.webarxsecurity.com/vulnerability-infinitewp-client-wp-time-capsule/) on WP Time Capsule < 1.21.16 . This PoC prove how the issue works and how it can be exploited.

The PoC

This POC offer two different options:

• Case 1 : grab the admin cookie Example:

    poc.py http://127.0.0.1/

• Case 2 : grab the admin cookie + upload a password protected webshell on /wp-content/plugins/shell/shell.php Example:

  poc.py http://127.0.0.1 shell

The issue

The function decode_server_request_wptc() , which is inside the wptc-cron-functions.php and is called by the Wptc_Init constructor does not perform any kind of privilege checking while decoding the requests sent on the body:

if( !empty($HTTP_RAW_POST_DATA_LOCAL)
  && strpos($HTTP_RAW_POST_DATA_LOCAL, 'IWP_JSON_PREFIX') !== false ){

  wptc_log('', "--------IWP_JSON_PREFIX--coming------");

  wp_cookie_constants();
  wptc_login_as_admin();
}

It simply checks that the body on any POST request contains the string IWP_JSON_PREFIX, if so , it calls the methods:

  wp_cookie_constants();
  wptc_login_as_admin();

wptc_login_as_admin() gets all the admin users, extract the first one and returns a cookie for that username.

function wptc_login_as_admin(){

    wptc_log(func_get_args(), "--------" . __FUNCTION__ . "--------");

    wptc_define_admin_constants();

    if( !function_exists('is_user_logged_in') ){
        include_once( ABSPATH . 'wp-includes/pluggable.php' );
    }

    if(is_user_logged_in()){
        return ;
    }

    $admins = get_users(array('role' => 'administrator'));

    foreach ($admins as $admin) {
        $user = $admin;
        break;
    }

    if (isset($user) && isset($user->ID)) {
        wp_set_current_user($user->ID);
        // Compatibility with All In One Security
        update_user_meta($user->ID, 'last_login_time', current_time('mysql'));
    }

    if(!defined('SECURE_AUTH_COOKIE')){

        return;
    }

    $isHTTPS = (bool)is_ssl();

    if($isHTTPS){
        wp_set_auth_cookie($user->ID);
    } else{
        wp_set_auth_cookie($user->ID, false, false);
        wp_set_auth_cookie($user->ID, false, true);
    }
}

Replicating the issue

For this test we used:

• A docker-compose ready Wordpress Image https://github.com/nezhar/wordpress-docker-compose
• wp-time-capsule 1.21.15 https://downloads.wordpress.org/plugin/wp-time-capsule.1.21.15.zip
• Burp Suite

Steps involved:

1. Access to a new session on the browser
2. Go to wp-login.php
3. Write dummy username and password
4. Replace any part of the BODY with the following string: IWP_JSON_PREFIX
5. Go back to the home page