CVE-2026-25364: Sprout Invoices Auth Bypass Vulnerability

CVE-2026-25364 Overview

CVE-2026-25364 is a Missing Authorization vulnerability affecting the Client Invoicing by Sprout Invoices WordPress plugin developed by BoldGrid. This broken access control flaw allows attackers to exploit incorrectly configured access control security levels, potentially enabling unauthorized users to perform privileged actions within the invoicing system. The vulnerability stems from CWE-862 (Missing Authorization), indicating that the plugin fails to properly verify user permissions before allowing access to sensitive functionality.

Critical Impact

Unauthorized users may be able to access, modify, or manipulate invoicing data and administrative functions without proper authentication or authorization checks.

Affected Products

• Client Invoicing by Sprout Invoices WordPress Plugin versions up to and including 20.8.8
• WordPress installations running vulnerable versions of the sprout-invoices plugin

Discovery Timeline

• 2026-02-19 - CVE-2026-25364 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-25364

Vulnerability Analysis

This vulnerability represents a Missing Authorization flaw (CWE-862) in the Sprout Invoices WordPress plugin. The core issue lies in the plugin's failure to implement proper authorization checks before granting access to protected resources or functionality. In WordPress plugin development, authorization checks typically involve verifying user capabilities using functions like current_user_can() or validating nonces for CSRF protection alongside permission verification.

When authorization checks are missing or improperly implemented, attackers can potentially access administrative endpoints, modify invoice data, view sensitive client information, or perform actions that should be restricted to authenticated administrators. This type of vulnerability is particularly dangerous in invoicing plugins as they handle sensitive financial and client data.

Root Cause

The root cause of CVE-2026-25364 is the absence of proper authorization verification within the Sprout Invoices plugin codebase. The plugin fails to adequately check whether the requesting user has the necessary permissions to perform specific actions. This typically occurs when developers implement AJAX handlers, REST API endpoints, or admin functions without wrapping them in appropriate capability checks. The vulnerability affects all versions from the initial release through version 20.8.8.

Attack Vector

An attacker can exploit this vulnerability by directly accessing plugin endpoints or invoking plugin functions without proper authorization. Since no authentication bypass is required (the authorization check itself is missing), an attacker with minimal access to the WordPress site—or in some cases, no authentication at all—could potentially:

1. Access administrative AJAX endpoints that handle invoice operations
2. Manipulate invoice records, payment statuses, or client data
3. View sensitive business and client information stored by the plugin
4. Potentially escalate privileges within the WordPress installation

The attack does not require user interaction and can be performed remotely against any WordPress installation running the vulnerable plugin versions.

Detection Methods for CVE-2026-25364

Indicators of Compromise

• Unusual access patterns to Sprout Invoices plugin endpoints from unauthenticated or low-privilege users
• Unexpected modifications to invoice records, client data, or plugin settings
• WordPress access logs showing requests to /wp-admin/admin-ajax.php with Sprout Invoices-related actions from suspicious IP addresses
• Anomalous changes in payment statuses or invoice amounts without corresponding administrative activity

Detection Strategies

• Monitor WordPress access logs for unauthorized requests to plugin-specific AJAX actions and REST endpoints
• Implement Web Application Firewall (WAF) rules to detect and block suspicious parameter patterns associated with Sprout Invoices functionality
• Review plugin activity logs for operations performed without corresponding admin session activity
• Deploy file integrity monitoring to detect unauthorized changes to plugin files

Monitoring Recommendations

• Enable comprehensive logging for all WordPress admin-ajax.php requests and filter for Sprout Invoices actions
• Configure alerting for invoice modifications outside normal business hours or from unexpected geographic locations
• Implement real-time monitoring for unauthorized access attempts to WordPress plugin endpoints
• Regularly audit user access patterns and compare against baseline normal behavior

How to Mitigate CVE-2026-25364

Immediate Actions Required

• Update the Client Invoicing by Sprout Invoices plugin to a patched version as soon as one becomes available
• Review recent invoice and client data modifications for any unauthorized changes
• Temporarily disable the Sprout Invoices plugin if the invoicing functionality is not immediately critical
• Implement additional WordPress security plugins that provide endpoint protection and access control logging

Patch Information

The vulnerability affects Client Invoicing by Sprout Invoices versions through 20.8.8. Site administrators should monitor for an updated release from BoldGrid that addresses this authorization bypass. For detailed vulnerability information and patch status, refer to the Patchstack Security Vulnerability Report.

Workarounds

• Restrict access to WordPress admin endpoints at the web server level using IP allowlisting for trusted administrators
• Implement a Web Application Firewall (WAF) with rules to block unauthorized requests to plugin endpoints
• Limit user registration and ensure minimal privilege assignments for all WordPress user accounts
• Consider temporarily disabling the plugin until an official patch is released if invoicing functionality can be handled through alternative means

# Example: Restrict admin-ajax.php access via .htaccess
<Files admin-ajax.php>
    <RequireAll>
        Require all granted
    </RequireAll>
</Files>

# Note: Full restriction may break legitimate AJAX functionality
# Consider implementing application-level controls instead