CVE-2025-57909

Executive Summary

CVE-2025-57909 is a Missing Authorization vulnerability in the Editor Custom Color Palette WordPress plugin by Rouergue Création, affecting versions through 3.5.6. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized modification of color palette settings or exposure of sensitive configuration data. The vulnerability is classified as a WordPress ecosystem issue, not related to Apache or Nginx. With a CVSS score of 6.5 (Medium), it poses a moderate risk, especially in multi-tenant or shared hosting environments. No public exploit code or proof-of-concept is currently available, and the patch status remains unknown.

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. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors leveraging this flaw in targeted attacks.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Impact confined to the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited information disclosure.
• Integrity Impact: Low (I:L) – Limited data modification.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. The vulnerability is easy to exploit remotely without authentication, but the impact is limited to low confidentiality and integrity loss. However, in a WordPress context, this could allow an attacker to alter color palette settings, potentially leading to stored XSS or defacement.

Deep Dive & Mechanics

The Editor Custom Color Palette plugin adds custom color palettes to the WordPress block editor (Gutenberg). The vulnerability stems from missing authorization checks on AJAX actions or REST API endpoints used to save or retrieve palette configurations. Specifically, the plugin fails to verify user capabilities (e.g., edit_posts or manage_options) before processing requests, allowing any unauthenticated visitor to:

• Modify the color palette settings.
• Retrieve sensitive configuration data (e.g., site-specific color codes).

The flaw is classified under CWE-862: Missing Authorization. The plugin likely registers AJAX hooks without proper nonce verification or capability checks, making it accessible to unauthenticated users.

Attack Vector:

1. An attacker sends a crafted HTTP request to the WordPress site (e.g., POST /wp-admin/admin-ajax.php with action update_color_palette).
2. The plugin processes the request without checking if the user has the required permissions.
3. The attacker can then modify the color palette or extract data.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is hypothesized based on common WordPress plugin mistakes:

Vulnerable Code (hypothetical):

add_action('wp_ajax_nopriv_update_color_palette', 'update_color_palette_callback');
add_action('wp_ajax_update_color_palette', 'update_color_palette_callback');

function update_color_palette_callback() {
    // Missing capability check
    $palette = $_POST['palette'];
    update_option('editor_custom_color_palette', $palette);
    wp_die();
}

Patched Code (hypothetical):

add_action('wp_ajax_update_color_palette', 'update_color_palette_callback');

function update_color_palette_callback() {
    // Added capability check
    if (!current_user_can('edit_posts')) {
        wp_die('Unauthorized', 403);
    }
    check_ajax_referer('editor_custom_color_palette_nonce', 'nonce');
    $palette = sanitize_text_field($_POST['palette']);
    update_option('editor_custom_color_palette', $palette);
    wp_die();
}

The patched version adds current_user_can('edit_posts') and nonce verification, restricting access to authenticated users with editing privileges.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with Editor Custom Color Palette plugin <= 3.5.6.
• No authentication required.

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., admin-ajax.php with action ecp_update_palette).
2. Send a crafted POST request to modify the palette:

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=ecp_update_palette&palette={\"colors\":[\"#ff0000\",\"#00ff00\"]}"

3. Verify the change by visiting the site's editor page.

Note: No public exploit code is available; this is a hypothetical example.

Blue Team (Detection & Defense)

Detection:

• Monitor for unusual POST requests to admin-ajax.php with unknown or suspicious actions.
• Look for requests lacking a valid nonce parameter.
• Alert on changes to the editor_custom_color_palette option in the database.

Defense:

• Disable the plugin until a patch is released.
• Implement a Web Application Firewall (WAF) rule to block unauthenticated requests to plugin-specific AJAX actions.
• Use a security plugin (e.g., Wordfence) to enforce capability checks.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-ajax.php with action parameter containing ecp_ or editor_custom_color_palette.
  • Requests without a valid _wpnonce parameter.
• File IOCs:
  • Modified wp-content/plugins/editor-custom-color-palette/ files (check file integrity).
• Database IOCs:
  • Unexpected values in the wp_options table under editor_custom_color_palette.
• Log IOCs:
  • Repeated 403 errors from admin-ajax.php if a WAF blocks the request.

Detection Engineering

YARA Rule

rule Detect_Editor_Custom_Color_Palette_Exploit {
    meta:
        description = "Detects exploitation attempts against CVE-2025-57909"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-57909"
    strings:
        $ajax_action = "ecp_update_palette" nocase
        $ajax_action2 = "editor_custom_color_palette" nocase
        $palette_param = "palette=" nocase
    condition:
        any of ($ajax_action*) and $palette_param
}

Sigma Rule

title: CVE-2025-57909 Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated POST requests to admin-ajax.php targeting Editor Custom Color Palette
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: POST
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains|all:
            - 'action=ecp_'
            - 'palette='
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-57909 - Editor Custom Color Palette Exploit"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=ecp_"; http_client_body; content:"palette="; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Implement a WAF rule to block unauthenticated requests to admin-ajax.php with actions containing ecp_.
3. Monitor logs for exploitation attempts.

Long-term Fix:

• Apply the vendor patch when available (check the WordPress plugin repository).
• If no patch is forthcoming, consider replacing the plugin with an alternative that has proper authorization checks.

Workaround:

• Add a custom code snippet to your theme's functions.php to enforce capability checks:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX) {
        if (isset($_POST['action']) && strpos($_POST['action'], 'ecp_') === 0) {
            if (!current_user_can('edit_posts')) {
                wp_die('Unauthorized', 403);
            }
        }
    }
});

Valters IT
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