CVE-2025-64229

Executive Summary

CVE-2025-64229 is a Missing Authorization vulnerability in the Client Invoicing by Sprout Invoices WordPress plugin (vendor: BoldGrid). This flaw allows an authenticated attacker with low privileges to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to sensitive invoice data or actions. The vulnerability affects all versions up to and including 20.8.7. 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 very low probability of exploitation in the wild at this time, but the risk remains for targeted attacks.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin distributed via the official WordPress plugin repository and third-party marketplaces. Users are advised to monitor for updates from BoldGrid and verify the integrity of plugin files using checksums provided by the repository. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): Low – An attacker needs a valid WordPress user account (e.g., subscriber).
• User Interaction (UI): None – No user action is needed.
• Scope (S): Unchanged – The exploit does not affect other components.
• Confidentiality (C): Low – Limited information disclosure (e.g., invoice details).
• Integrity (I): None – No data modification.
• Availability (A): None – No denial of service.

Threat Level: Medium. While the CVSS score is moderate, the lack of a patch and the potential for data leakage in a business context (invoices) elevates the risk for organizations using this plugin.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the sprout-invoices plugin. Specifically, certain AJAX actions or REST API endpoints do not properly verify that the requesting user has the required capabilities (e.g., edit_posts, manage_options) before processing requests. This allows an authenticated user with minimal privileges (e.g., a subscriber) to access or manipulate invoice data that should be restricted to administrators or shop managers.

Root Cause: The plugin fails to call current_user_can() or similar WordPress capability checks on sensitive functions. For example, a function like sprout_invoices_get_invoice_details() might be hooked to an AJAX action without verifying the user’s role.

Attack Scenario:

1. An attacker registers or compromises a low-privileged WordPress account (e.g., subscriber).
2. The attacker crafts a request to a vulnerable endpoint, such as /wp-admin/admin-ajax.php?action=si_get_invoice&invoice_id=123.
3. The plugin processes the request and returns sensitive invoice data (e.g., client names, amounts, payment status) without checking if the user has permission to view that invoice.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common fixes for missing authorization vulnerabilities.

Vulnerable Code (Example):

add_action('wp_ajax_si_get_invoice', 'si_get_invoice_callback');
function si_get_invoice_callback() {
    $invoice_id = intval($_GET['invoice_id']);
    $invoice = get_post($invoice_id);
    // Missing capability check
    wp_send_json_success($invoice);
}

Patched Code (Hypothetical):

add_action('wp_ajax_si_get_invoice', 'si_get_invoice_callback');
function si_get_invoice_callback() {
    if (!current_user_can('edit_posts')) {
        wp_die('Unauthorized', 403);
    }
    $invoice_id = intval($_GET['invoice_id']);
    $invoice = get_post($invoice_id);
    wp_send_json_success($invoice);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress instance with the vulnerable plugin (version <= 20.8.7).
• A low-privileged user account (e.g., subscriber).

Steps:

1. Log in as the low-privileged user.
2. Identify vulnerable endpoints by reviewing plugin source code or using a tool like Burp Suite to intercept AJAX requests.
3. Send a crafted request to a vulnerable endpoint. Example using curl:

   curl -c cookies.txt -b cookies.txt \
     "http://target.com/wp-admin/admin-ajax.php?action=si_get_invoice&invoice_id=1"
   

4. If successful, the response will contain invoice data that should be restricted.

Note: No public exploit code is available. The above is a generic example.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual AJAX requests from low-privileged users to plugin-specific actions (e.g., si_get_invoice, si_update_invoice).
• Look for HTTP 200 responses to unauthorized requests that return JSON data.

Hardening:

• Apply the principle of least privilege: ensure users have only the roles they need.
• Use a Web Application Firewall (WAF) to block requests to unknown or suspicious AJAX actions.
• Temporarily disable the plugin if it is not critical, until a patch is released.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-admin/admin-ajax.php with action parameters like si_get_invoice, si_list_invoices, or si_export_invoices.
  • Unusual JSON responses containing invoice data (e.g., {"success":true,"data":{"post_title":"Invoice #123"}}).
• File IOCs:
  • Modified plugin files (e.g., wp-content/plugins/sprout-invoices/). Check for unauthorized changes.
• Log IOCs:
  • WordPress debug logs showing wp_ajax_ calls from unexpected user roles.

Detection Engineering

YARA Rule

rule CVE_2025_64229_Sprout_Invoices_Missing_Auth {
    meta:
        description = "Detects missing authorization in Sprout Invoices plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-64229"
    strings:
        $func1 = "si_get_invoice" ascii wide nocase
        $func2 = "si_update_invoice" ascii wide nocase
        $func3 = "current_user_can" ascii wide nocase
        $func4 = "wp_ajax_" ascii wide nocase
    condition:
        (any of ($func1, $func2)) and not $func3 and $func4
}

Sigma Rule

title: CVE-2025-64229 - Missing Authorization in Sprout Invoices
id: 8a3f7c2e-5d1b-4a9f-8c6e-2b1d3f4a5c6d
status: experimental
description: Detects exploitation attempts of missing authorization in Sprout Invoices plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains:
            - "action=si_get_invoice"
            - "action=si_list_invoices"
            - "action=si_export_invoices"
    condition: selection
falsepositives:
    - Legitimate admin actions
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-64229 - Sprout Invoices Missing Authorization Attempt"; flow:to_server,established; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=si_"; http_uri; nocase; pcre:"/(si_get_invoice|si_list_invoices|si_export_invoices)/Ui"; classtype:attempted-recon; sid:10000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if it is not essential for business operations.
2. Restrict access to the plugin’s admin pages using a security plugin (e.g., Wordfence) or .htaccess rules.
3. Monitor for any unauthorized access attempts using the provided detection rules.

Long-Term Fix:

• Await an official patch from BoldGrid. Once released, update to the patched version immediately.
• If the plugin is custom-developed, apply the fix by adding current_user_can() checks to all AJAX and REST endpoints.

Workaround:

• Use a WordPress role editor plugin to remove unnecessary capabilities from low-privileged roles.
• Implement a Web Application Firewall (WAF) rule to block requests to vulnerable endpoints from non-admin users.

Valters IT
Securing Digital Frontiers