CVE-2024-1293

Executive Summary

CVE-2024-1293 is a Stored Cross-Site Scripting (XSS) vulnerability in the Brizy – Page Builder plugin for WordPress, affecting all versions up to and including 2.4.40. The flaw resides in the embedded media custom block, where insufficient input sanitization and output escaping allow authenticated attackers with contributor-level access or higher to inject arbitrary web scripts. These scripts execute whenever a user accesses a page containing the malicious block. The vulnerability has a CVSS score of 6.4 (Medium), with a low EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should monitor the plugin’s update channel for a patched version. No direct supply chain compromise of the plugin’s source code has been reported.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.4 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Contributor)
• User Interaction: Required (Victim must visit the page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. The vulnerability requires authentication and user interaction, but successful exploitation can lead to session hijacking, defacement, or phishing within the WordPress context.

Deep Dive & Mechanics

The vulnerability exists in the Brizy page builder’s handling of the “embedded media custom block.” When a user with contributor-level access or higher inserts a custom media block (e.g., video, audio, or iframe), the plugin fails to properly sanitize the input and escape the output. This allows an attacker to inject malicious JavaScript or HTML into the block’s attributes or content.

Root Cause: The plugin uses wp_kses or similar functions inadequately, or directly outputs user-supplied data without proper escaping. Specifically, the src attribute of an iframe or the data-* attributes of a custom block may be vulnerable.

Attack Flow:

1. Attacker logs in as a contributor or higher.
2. Creates or edits a page/post using Brizy.
3. Adds an embedded media custom block.
4. Injects a malicious payload (e.g., <script>alert('XSS')</script>) into a vulnerable field (e.g., URL or custom attribute).
5. Saves the page.
6. Any user (including admins) visiting the page triggers the script.

Impact: Stored XSS can lead to:

• Theft of admin session cookies.
• Defacement of the site.
• Redirection to malicious sites.
• Installation of backdoors via admin-level actions.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common fixes for similar XSS vulnerabilities.

Vulnerable Code (Brizy <= 2.4.40):

// In a block render function
$src = $_POST['media_url']; // No sanitization
echo '<iframe src="' . $src . '"></iframe>'; // No escaping

Patched Code (Hypothetical):

// In a block render function
$src = sanitize_url($_POST['media_url']); // Sanitize URL
echo '<iframe src="' . esc_url($src) . '"></iframe>'; // Escape output

Key Differences:

• Use of sanitize_url() to strip malicious content.
• Use of esc_url() to ensure safe output.
• Additional validation of allowed protocols (e.g., only https://).

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with Brizy plugin <= 2.4.40.
• Contributor-level account or higher.

Steps:

1. Log in to WordPress as a contributor.
2. Create a new page and open it with Brizy editor.
3. Add an “Embedded Media” block.
4. In the URL field, enter a malicious payload:

   javascript:alert(document.cookie)
   

   Or use an event handler:

   " onload="alert('XSS')
   

5. Save and publish the page.
6. Share the page link with a victim.

Example Payload (if iframe src is vulnerable):

<iframe src="javascript:alert('XSS')"></iframe>

Note: No public exploit code is available; this is a conceptual demonstration.

Blue Team (Detection & Prevention)

Detection:

• Monitor for pages created by contributors containing unusual iframe or script tags.
• Use Web Application Firewall (WAF) rules to block common XSS patterns in POST requests to Brizy endpoints.

Prevention:

• Restrict contributor-level access to trusted users only.
• Implement Content Security Policy (CSP) headers to block inline scripts.
• Use a WordPress security plugin to monitor file changes and user actions.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /wp-admin/admin-ajax.php with action brizy_* containing suspicious media_url parameters.
  • Outbound connections to attacker-controlled domains from compromised pages.

• Host IOCs:

  • Presence of unexpected <script> tags or event handlers in page content.
  • Modified database entries in wp_posts table with malicious JavaScript.

• File IOCs:

  • Modified plugin files (e.g., brizy/public/editor-build/...).

Detection Engineering

YARA Rule

rule Brizy_Stored_XSS_CVE_2024_1293 {
    meta:
        description = "Detects malicious payloads targeting Brizy plugin stored XSS"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-1293"
    strings:
        $xss1 = /<iframe[^>]+src\s*=\s*["']javascript:/i
        $xss2 = /onload\s*=\s*["']alert/i
        $xss3 = /onerror\s*=\s*["']alert/i
    condition:
        any of them
}

Sigma Rule

title: Brizy Stored XSS Detection
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential stored XSS attempts via Brizy plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: '/wp-admin/admin-ajax.php'
        cs-method: 'POST'
        cs-uri-query|contains: 'action=brizy_'
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate use of Brizy media blocks
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-1293 Brizy Stored XSS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=brizy_"; http_client_body; pcre:"/(<iframe[^>]+src\s*=\s*[\x22\x27]javascript:|onload\s*=\s*[\x22\x27]alert)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Brizy plugin until a patch is released.
2. Restrict contributor roles to only trusted users.
3. Implement a Web Application Firewall (WAF) with rules to block XSS payloads.

Long-term Fix:

• Apply the official patch once released by the vendor.
• Update to the latest version of Brizy (if patched).
• Conduct a security audit of all pages created by contributors.

Workarounds:

• Use a WordPress security plugin (e.g., Wordfence) to block malicious input.
• Manually review and sanitize any embedded media blocks in existing pages.

Valters IT
Securing Digital Frontiers