CVE-2025-66141

Executive Summary

CVE-2025-66141 is a Missing Authorization vulnerability in the Merkulove Scroller WordPress plugin, affecting versions up to and including 2.0.2. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or modification. The vulnerability is classified under CWE-862 (Missing Authorization) and carries a CVSS score of 5.4 (Medium). As of this report, no official patch has been released, and no public proof-of-concept (PoC) or exploit code is available. The EPSS score is 0.0%, indicating a low probability of exploitation in the wild at this time.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository and potentially third-party marketplaces. Users are advised to monitor the plugin’s update channel and consider disabling the plugin until a patch is released.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited data modification.
• Availability (A): None (N) – No denial-of-service impact.

Threat Level: Medium. The vulnerability is easy to exploit but has limited impact.

Deep Dive & Mechanics

The Merkulove Scroller plugin fails to properly enforce authorization checks on certain AJAX actions or REST API endpoints. This allows an unauthenticated attacker to invoke functions that should require administrative or editor-level privileges. The missing authorization check likely occurs in a function that handles scrolling content updates, settings modifications, or data retrieval.

Root Cause: The plugin does not call current_user_can() or similar WordPress capability checks before executing sensitive operations. This is a classic example of Insecure Direct Object Reference (IDOR) or Missing Function Level Access Control.

Attack Vector: An attacker can send crafted HTTP requests to the vulnerable endpoint, bypassing authentication and performing actions such as:

• Modifying plugin settings.
• Accessing or deleting stored scrolling content.
• Potentially injecting malicious data.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common fixes for this type of vulnerability.

Vulnerable Code (hypothetical):

add_action('wp_ajax_scroller_update', 'scroller_update_handler');
add_action('wp_ajax_nopriv_scroller_update', 'scroller_update_handler'); // Missing capability check

function scroller_update_handler() {
    // Process request without checking user capabilities
    update_option('scroller_settings', $_POST['settings']);
    wp_die();
}

Patched Code (hypothetical):

add_action('wp_ajax_scroller_update', 'scroller_update_handler');
// Remove the nopriv hook to require authentication

function scroller_update_handler() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    // Process request
    update_option('scroller_settings', $_POST['settings']);
    wp_die();
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with Scroller plugin <= 2.0.2.
• Network access to the site.

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /wp-admin/admin-ajax.php?action=scroller_update).
2. Send a crafted POST request without authentication:

   curl -X POST http://target/wp-admin/admin-ajax.php \
     -d "action=scroller_update&settings[malicious]=value"
   

3. Verify unauthorized modification of plugin settings.

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

Blue Team (Detection & Defense)

Detection:

• Monitor for unusual AJAX requests to admin-ajax.php with actions related to the Scroller plugin.
• Look for requests lacking authentication cookies or nonces.

Defense:

• Disable the plugin until a patch is released.
• Implement Web Application Firewall (WAF) rules to block unauthenticated requests to known vulnerable endpoints.
• Use WordPress security plugins to enforce capability checks.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /wp-admin/admin-ajax.php with action=scroller_* parameters.
  • Requests missing Cookie: wordpress_logged_in_* headers.
• File IOCs:
  • Modified plugin files in /wp-content/plugins/scroller/.
  • Unexpected entries in wp_options table related to scroller_settings.
• Log IOCs:
  • Repeated 403 errors from admin-ajax.php if WAF blocks attempts.
  • Unusual user agent strings in access logs.

Detection Engineering

YARA Rule

rule CVE_2025_66141_Scroller_Missing_Auth {
    meta:
        description = "Detects missing authorization in Merkulove Scroller plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-66141"
    strings:
        $vuln_func = "wp_ajax_nopriv_scroller" nocase
        $vuln_action = "scroller_update" nocase
    condition:
        any of ($vuln_func) or any of ($vuln_action)
}

Sigma Rule

title: CVE-2025-66141 - Missing Authorization in Merkulove Scroller
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated AJAX requests to Scroller plugin endpoints
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=scroller_'
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate admin requests (rare)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-66141 - Scroller Missing Authorization Attempt"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=scroller_"; http_client_body; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Implement a WAF rule to block unauthenticated requests to admin-ajax.php with action=scroller_*.
3. Monitor logs for exploitation attempts.

Long-term Fix:

• The vendor must release a patched version that adds proper capability checks (e.g., current_user_can('manage_options')) to all AJAX handlers.
• Users should update to the latest version once available.

Workaround:

• Add the following code to the theme’s functions.php to block unauthenticated access:

  add_action('init', function() {
      if (defined('DOING_AJAX') && DOING_AJAX) {
          $action = $_REQUEST['action'] ?? '';
          if (strpos($action, 'scroller_') === 0 && !is_user_logged_in()) {
              wp_die('Unauthorized', 403);
          }
      }
  });
  

Valters IT
Securing Digital Frontiers