CVE-2025-30993

Executive Summary

CVE-2025-30993 is a Missing Authorization vulnerability in the VillaTheme Thank You Page Customizer for WooCommerce plugin (slug: woo-thank-you-page-customizer). This flaw allows unauthenticated attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized modification of WooCommerce thank-you page settings. The vulnerability affects all versions up to and including 1.1.7. No official patch has been released by the vendor, and no public exploit code or proof-of-concept is currently available. The CVSS score of 6.5 (Medium) reflects the ease of exploitation (network-based, low complexity, no privileges required) but limited impact on confidentiality and integrity.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin via the WordPress admin dashboard or directly from the repository are affected. No supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors injecting backdoors or exploiting the vulnerability in the wild.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Exploit does not affect other components.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited data modification.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The vulnerability is easy to exploit but has limited impact. However, the absence of a patch and the potential for chaining with other vulnerabilities elevates the risk.

Deep Dive & Mechanics

The vulnerability stems from a missing authorization check in the plugin’s AJAX handlers or REST API endpoints. The plugin likely registers actions (e.g., wp_ajax_* or wp_ajax_nopriv_*) that allow saving or modifying thank-you page templates, custom CSS, or redirect URLs without verifying the user’s capabilities (e.g., manage_options or edit_theme_options). An unauthenticated attacker can send crafted HTTP requests to these endpoints to alter the thank-you page content, potentially injecting malicious scripts, redirecting users to phishing sites, or defacing the page.

The core issue is that the plugin uses current_user_can() incorrectly or not at all for certain actions. For example, a function like save_thank_you_settings() might be hooked to wp_ajax_nopriv_* (allowing unauthenticated access) or the capability check is missing entirely.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is hypothesized based on common WordPress plugin authorization flaws.

Vulnerable Code (hypothetical):

add_action('wp_ajax_nopriv_save_thank_you_settings', 'save_thank_you_settings');
function save_thank_you_settings() {
    // Missing capability check
    update_option('typc_settings', $_POST['settings']);
    wp_send_json_success();
}

Patched Code (hypothetical):

add_action('wp_ajax_save_thank_you_settings', 'save_thank_you_settings');
function save_thank_you_settings() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    update_option('typc_settings', $_POST['settings']);
    wp_send_json_success();
}

The patch would require moving the action from wp_ajax_nopriv_* to wp_ajax_* (authenticated only) and adding a capability check.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with woo-thank-you-page-customizer <= 1.1.7 installed and activated.
• No authentication required.

Exploitation Steps:

1. Identify the vulnerable endpoint. Common patterns include /wp-admin/admin-ajax.php?action=typc_save_settings or a custom REST route.
2. Send a POST request with malicious payload:

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=typc_save_settings&settings[redirect_url]=https://evil.com/phishing"

3. Verify the change by visiting the WooCommerce thank-you page.

Note: No public exploit code exists; this is a theoretical approach.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual POST requests to /wp-admin/admin-ajax.php with action parameters related to typc_, thank_you, or woo-thank-you.
• Look for unauthenticated requests modifying WordPress options (e.g., update_option calls).

Hardening:

• Disable the plugin until a patch is available.
• Use a Web Application Firewall (WAF) to block requests to unknown AJAX actions.
• Implement a custom plugin that adds capability checks to all AJAX hooks.

Indicators of Compromise (IOCs)

• Network: POST requests to /wp-admin/admin-ajax.php with action=typc_* from unauthenticated IPs.
• File: Modified wp_options table entries with typc_settings or similar option names.
• Behavior: Unexpected changes to WooCommerce thank-you page content, redirects, or injected scripts.
• Logs: WordPress debug log entries showing wp_ajax_nopriv_* calls without authentication.

Detection Engineering

YARA Rule

rule CVE_2025_30993_WordPress_Plugin {
    meta:
        description = "Detects vulnerable Thank You Page Customizer plugin files"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-30993"
    strings:
        $ajax_hook = "wp_ajax_nopriv_" nocase
        $function = "save_thank_you_settings" nocase
        $missing_cap = "current_user_can" nocase
    condition:
        $ajax_hook and $function and not $missing_cap
}

Sigma Rule

title: CVE-2025-30993 - Unauthenticated AJAX Request to Thank You Page Customizer
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects unauthenticated POST requests to wp-admin/admin-ajax.php with action parameters related to the vulnerable plugin.
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains|all:
            - 'action=typc_'
            - 'action=thank_you'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"CVE-2025-30993 - Unauthenticated AJAX Request to Thank You Page Customizer";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=typc_"; http_client_body;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Implement a WAF rule to block requests to /wp-admin/admin-ajax.php with action parameters starting with typc_ from unauthenticated users.
3. Monitor logs for exploitation attempts.

Long-term Fix:

• The vendor must release a patched version that adds proper capability checks (e.g., current_user_can('manage_options')) and moves AJAX hooks to authenticated-only endpoints.
• Users should apply the patch as soon as it becomes available.

Workaround:

• Add the following code to the theme’s functions.php to block unauthenticated access to the vulnerable endpoints:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX && !is_user_logged_in()) {
        $action = $_REQUEST['action'] ?? '';
        if (strpos($action, 'typc_') === 0) {
            wp_die('Unauthorized', 403);
        }
    }
});

Valters IT
Securing Digital Frontiers