CVE-2025-48270

Executive Summary

CVE-2025-48270 is a DOM-Based Cross-Site Scripting (XSS) vulnerability in the SKT Blocks WordPress plugin (versions up to and including 2.2), developed by Sktthemes. This flaw allows an attacker to inject malicious scripts into a web page’s Document Object Model (DOM) without proper sanitization of user-controlled input. The vulnerability is triggered entirely on the client side, meaning the server does not reflect the payload, making it harder to detect via traditional server-side logging. Given the CVSS score of 6.5 (Medium) and the EPSS score of 0.0%, exploitation is currently not widespread, but the lack of a patch increases risk for sites using this plugin. As a WordPress plugin vulnerability, it directly impacts the WordPress ecosystem and should be treated as a WordPress-specific issue.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. The plugin is not an NPM, PyPI, Go, or Ruby package, but it is part of the WordPress supply chain. Users should verify the integrity of the plugin files and monitor for updates from the vendor. Since no patch is available, the supply chain risk is elevated, and users should consider removing the plugin until a fix is released.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – The victim must click a crafted link or visit a malicious 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): None (N) – No impact on availability.

Threat Level: Medium. The vulnerability requires user interaction, but the lack of a patch and the widespread use of WordPress make it a credible threat for targeted attacks.

Deep Dive & Mechanics

The vulnerability resides in the SKT Blocks plugin, which provides custom Gutenberg blocks for WordPress. The issue is a DOM-Based XSS, meaning the malicious payload is executed by the browser’s JavaScript engine after the page has loaded, without the server processing the malicious input. This typically occurs when the plugin reads data from the URL fragment (hash) or other DOM sources and writes it directly into the page without sanitization.

Root Cause: The plugin fails to properly neutralize user input when generating web pages. Specifically, it likely uses document.location.hash or document.URL to dynamically insert content into the DOM via innerHTML or similar methods, without encoding or escaping the input.

Attack Flow:

1. Attacker crafts a URL with a malicious payload in the fragment identifier (e.g., https://victim.com/#<img src=x onerror=alert(1)>).
2. Victim clicks the link or is redirected to the crafted URL.
3. The SKT Blocks plugin’s JavaScript reads the fragment and injects it into the DOM.
4. The browser executes the injected script, leading to XSS.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable code likely resembles:

// Vulnerable code in skt-blocks.js
var hash = window.location.hash;
document.getElementById('some-element').innerHTML = hash;

A patched version would sanitize the input:

// Patched code
var hash = window.location.hash;
var safeHash = document.createTextNode(hash);
document.getElementById('some-element').appendChild(safeHash);

Or use a DOMPurify library:

var hash = window.location.hash;
document.getElementById('some-element').innerHTML = DOMPurify.sanitize(hash);

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Target: WordPress site with SKT Blocks plugin version 2.2.
• Attacker: Kali Linux with browser and Burp Suite.

Exploitation Steps:

1. Identify a page that uses SKT Blocks (e.g., a page with a custom block).
2. Craft a malicious URL:

   http://victim.com/wordpress/?page_id=123#<img src=x onerror=alert(document.cookie)>
   

3. Send the link to the victim via phishing email or social engineering.
4. When the victim clicks the link, the XSS payload executes, stealing cookies or performing actions on behalf of the victim.

Proof-of-Concept (PoC):

<!-- PoC HTML file to simulate the attack -->
<a href="http://victim.com/wordpress/?page_id=123#<img src=x onerror=alert('XSS')>">Click me</a>

Blue Team (Defensive)

Detection:

• Monitor web logs for URLs containing # followed by suspicious characters (e.g., <, >, onerror).
• Use browser-based security headers like Content-Security-Policy to block inline scripts.

Mitigation:

• Remove or disable the SKT Blocks plugin until a patch is available.
• Implement a Web Application Firewall (WAF) rule to block requests with suspicious fragment identifiers.
• Educate users about phishing links.

Indicators of Compromise (IOCs)

• Network IOCs:
  • URLs containing #<script> or #<img patterns.
  • Referer headers from known malicious domains.
• Host IOCs:
  • Presence of skt-blocks plugin in /wp-content/plugins/skt-blocks/.
  • Modified JavaScript files in the plugin directory.
• Behavioral IOCs:
  • Unexpected JavaScript execution in the browser.
  • Unauthorized cookie theft or session hijacking.

Detection Engineering

YARA Rule

rule CVE_2025_48270_DOM_XSS {
    meta:
        description = "Detects DOM-based XSS in SKT Blocks plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-48270"
    strings:
        $s1 = "window.location.hash" ascii wide nocase
        $s2 = "innerHTML" ascii wide nocase
        $s3 = "skt-blocks" ascii wide nocase
    condition:
        all of ($s1, $s2, $s3)
}

Sigma Rule

title: CVE-2025-48270 DOM-Based XSS in SKT Blocks
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of DOM-based XSS in SKT Blocks plugin
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: '#<'
    condition: selection
falsepositives:
    - Legitimate use of hash fragments with HTML characters
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-48270 DOM-Based XSS in SKT Blocks"; flow:to_server,established; content:"#<"; http_uri; pcre:"/#<[^>]*>/i"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable or remove the SKT Blocks plugin from all WordPress installations until a patched version is released.
2. Workaround: If the plugin is critical, implement a Content Security Policy (CSP) that blocks inline scripts:

   Content-Security-Policy: script-src 'self' https://trusted-cdn.com;
   

3. Long-term Fix: The vendor must release a patched version that sanitizes all DOM inputs. Users should monitor the WordPress plugin repository for updates.
4. Monitoring: Enable logging of all HTTP requests and review for suspicious hash fragments.
5. User Training: Educate users not to click on suspicious links, especially those containing # followed by HTML tags.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert