CVE-2025-55715

Executive Summary

CVE-2025-55715 is a critical information disclosure vulnerability in the WordPress plugin Otter - Gutenberg Blocks (slug: otter-blocks) by Themeisle, affecting versions up to and including 3.1.0. The vulnerability allows an unauthenticated attacker to retrieve embedded sensitive data from the server, such as API keys, database credentials, or other secrets that are inadvertently included in sent data. This is classified as an Insertion of Sensitive Information Into Sent Data (CWE-201) flaw, with a CVSS score of 7.5 (High). The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the lack of a patch makes this a significant risk for all WordPress sites using this plugin.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory and can be installed directly from the WordPress admin dashboard or via Composer. Since no patch is available, users must consider removing or disabling the plugin immediately. The plugin's source code is publicly available on the WordPress SVN repository, allowing for manual inspection and potential hotfixing.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – Sensitive data is exposed.
• Integrity Impact: None (I:N) – Data integrity is not compromised.
• Availability Impact: None (A:N) – Service availability is not affected.

Threat Level: High. The vulnerability is trivial to exploit and exposes sensitive data, but the lack of a public PoC and low EPSS score currently reduce immediate risk.

Deep Dive & Mechanics

The vulnerability resides in the otter-blocks plugin, specifically in how it handles data sent to the client. The plugin likely exposes sensitive information (e.g., API keys, nonces, or internal paths) in JavaScript variables, HTTP headers, or AJAX responses. This is a classic case of information disclosure where the plugin includes sensitive data in the output that should be restricted to server-side processing.

Root Cause: The plugin fails to sanitize or restrict the data included in responses to client-side requests. For example, it might expose the wp-config.php database credentials, REST API nonces, or third-party service API keys in the page source or AJAX responses.

Attack Vector: An unauthenticated attacker can send a crafted HTTP request to a vulnerable endpoint (e.g., a REST API route or a specific page) and receive sensitive data in the response. No special privileges or user interaction are required.

Impact: Successful exploitation allows an attacker to retrieve embedded sensitive data, which could lead to further compromise of the WordPress site, including database access, privilege escalation, or lateral movement to connected services.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code. The following is a hypothetical example of the vulnerable pattern:

Vulnerable Code (otter-blocks <= 3.1.0):

// In a REST API endpoint or AJAX handler
function otter_get_sensitive_data() {
    $api_key = get_option('otter_api_key'); // Sensitive data
    wp_send_json_success(array('api_key' => $api_key)); // Exposed!
}

Patched Code (Hypothetical):

function otter_get_sensitive_data() {
    // Do not expose sensitive data
    wp_send_json_success(array('status' => 'ok'));
}

Key Difference: The patched version would remove any sensitive data from the response or implement proper access controls.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• A WordPress site with Otter Blocks plugin version <= 3.1.0 installed and active.
• Network access to the target.

Exploitation Steps:

1. Identify the vulnerable endpoint. Common targets include:
   • /wp-json/otter/v1/settings
   • /wp-admin/admin-ajax.php?action=otter_get_data
2. Send a GET or POST request to the endpoint.
3. Parse the response for sensitive data (e.g., API keys, database credentials).

Example using cURL:

curl -X GET "http://target.com/wp-json/otter/v1/settings" -H "User-Agent: Mozilla/5.0"

Expected Output:

{
  "success": true,
  "data": {
    "api_key": "sk-xxxxxxxxxxxxxxxx",
    "db_password": "secret123"
  }
}

Blue Team (Defender)

Detection:

• Monitor for unusual requests to /wp-json/otter/v1/* or admin-ajax.php with action=otter_*.
• Look for responses containing patterns like api_key, secret, password, or token.

Mitigation:

• Immediately disable or remove the otter-blocks plugin.
• Implement a Web Application Firewall (WAF) rule to block requests to known vulnerable endpoints.
• Rotate any exposed credentials (API keys, database passwords, etc.).

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-json/otter/v1/settings or similar endpoints.
  • Responses containing JSON with keys like api_key, secret, password.
• File IOCs:
  • Presence of the otter-blocks plugin directory at /wp-content/plugins/otter-blocks/.
• Log IOCs:
  • Unusual 200 OK responses to unauthenticated REST API requests.
  • Repeated requests from the same IP to plugin-specific endpoints.

Detection Engineering

YARA Rule

rule CVE_2025_55715_Otter_Blocks_Info_Disclosure {
    meta:
        description = "Detects sensitive data exposure in Otter Blocks plugin responses"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-55715"
    strings:
        $sensitive1 = /"api_key"\s*:\s*"[^"]+"/ nocase
        $sensitive2 = /"secret"\s*:\s*"[^"]+"/ nocase
        $sensitive3 = /"password"\s*:\s*"[^"]+"/ nocase
        $endpoint = "/wp-json/otter/v1/" nocase
    condition:
        $endpoint and any of ($sensitive*)
}

Sigma Rule

title: CVE-2025-55715 - Otter Blocks Sensitive Data Exposure
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP responses containing sensitive data from Otter Blocks plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: 
            - "/wp-json/otter/v1/"
            - "action=otter_"
        sc-status: 200
        response_body|contains:
            - "api_key"
            - "secret"
            - "password"
    condition: selection
falsepositives:
    - Legitimate plugin functionality (if any)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-55715 - Otter Blocks Sensitive Data Exposure"; flow:to_server; content:"/wp-json/otter/v1/"; http_uri; nocase; content:"api_key"; http_server_body; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin: Deactivate and delete the otter-blocks plugin from the WordPress admin dashboard.
2. Rotate credentials: Change all API keys, database passwords, and other secrets that may have been exposed.
3. Monitor logs: Review web server and application logs for signs of exploitation.

Long-term Fix:

• Wait for an official patch from Themeisle. Monitor the WordPress Plugin Directory for updates.
• If you must use the plugin, consider implementing a custom patch by removing sensitive data from all output functions.

Workaround:

• Use a Web Application Firewall (WAF) to block requests to /wp-json/otter/v1/* and admin-ajax.php with action=otter_*.
• Implement a .htaccess rule to deny access to the plugin's REST API endpoints:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteRule ^wp-json/otter/v1/ - [F,L]
</IfModule>

Valters IT
Securing Digital Frontiers