CVE-2026-1748: Invoct WordPress Plugin Data Disclosure Flaw

CVE-2026-1748 Overview

CVE-2026-1748 is a Missing Authorization vulnerability (CWE-862) affecting the Invoct – PDF Invoices & Billing for WooCommerce plugin for WordPress. The vulnerability exists due to missing capability checks on multiple functions in all versions up to, and including, 1.6. This security flaw enables authenticated attackers with Subscriber-level access and above to retrieve sensitive data including invoice clients, invoice items, and a list of WordPress users along with their email addresses.

Critical Impact

Authenticated attackers with minimal privileges (Subscriber-level) can access sensitive customer invoice data and harvest WordPress user emails, potentially enabling further targeted attacks or data breaches.

Affected Products

• Invoct – PDF Invoices & Billing for WooCommerce plugin for WordPress versions up to and including 1.6
• WordPress installations using the kirilkirkov-pdf-invoice-manager plugin
• WooCommerce-powered sites with the vulnerable plugin installed

Discovery Timeline

• 2026-02-11 - CVE-2026-1748 published to NVD
• 2026-02-11 - Last updated in NVD database

Technical Details for CVE-2026-1748

Vulnerability Analysis

This vulnerability represents a classic Broken Access Control flaw where critical functions within the plugin fail to verify that the requesting user has appropriate permissions before returning sensitive data. The plugin exposes multiple AJAX endpoints that process requests without validating whether the authenticated user has the necessary capabilities to access the requested information.

In WordPress's security model, capability checks are essential for ensuring that users can only access functionality appropriate to their role. The Invoct plugin omits these checks on functions responsible for retrieving invoice clients, invoice items, and WordPress user listings. This allows any authenticated user—including those with the lowest privilege level (Subscriber)—to invoke these functions and exfiltrate data that should be restricted to administrators or shop managers.

The exposure of user email addresses is particularly concerning as it can facilitate phishing campaigns, spam, or credential stuffing attacks against the site's user base.

Root Cause

The root cause is the absence of capability verification calls (such as current_user_can()) in the vulnerable functions within the KirilKirkovWpInvoices.php file. Multiple functions at lines 565, 585, 605, and 626 process AJAX requests without first confirming that the requesting user possesses the required administrative capabilities. This design oversight allows any authenticated user to bypass intended access restrictions.

Attack Vector

The attack is network-based and requires only a valid authenticated session with minimal privileges. An attacker would:

1. Register or compromise a WordPress account with Subscriber-level access on a target site
2. Authenticate to the WordPress dashboard
3. Craft AJAX requests to the vulnerable plugin endpoints
4. Retrieve unauthorized data including invoice clients, invoice items, and user email listings

The vulnerability mechanism involves direct invocation of unprotected AJAX handlers. An attacker sends crafted POST requests to the WordPress AJAX endpoint (/wp-admin/admin-ajax.php) specifying the vulnerable action names. Without capability checks, the plugin processes these requests and returns sensitive data. For detailed technical analysis, refer to the Wordfence vulnerability report and the plugin source code.

Detection Methods for CVE-2026-1748

Indicators of Compromise

• Unusual AJAX requests to admin-ajax.php from low-privilege user sessions
• Subscriber or Customer-level accounts accessing invoice-related AJAX actions
• Bulk retrieval of user data or invoice information from non-administrative accounts
• Unexpected database queries for invoice clients, items, or user listings originating from plugin functions

Detection Strategies

• Monitor WordPress AJAX request logs for invoice-related action parameters from non-admin users
• Implement Web Application Firewall (WAF) rules to flag suspicious patterns in AJAX requests to the plugin endpoints
• Review access logs for repeated requests to admin-ajax.php with invoice-related action names from low-privilege sessions
• Deploy file integrity monitoring to detect unauthorized changes to the plugin files

Monitoring Recommendations

• Enable detailed logging for WordPress AJAX requests and correlate with user role data
• Configure alerts for data exfiltration patterns such as bulk user email retrieval
• Regularly audit user accounts to identify any unauthorized privilege escalation or suspicious activity
• Monitor for unusual traffic patterns to WooCommerce invoice-related endpoints

How to Mitigate CVE-2026-1748

Immediate Actions Required

• Update the Invoct – PDF Invoices & Billing for WooCommerce plugin to a version newer than 1.6 that includes capability checks
• Temporarily deactivate the plugin if an update is not immediately available
• Audit WordPress user accounts for any suspicious Subscriber-level accounts that may have been created by attackers
• Review server logs for signs of exploitation targeting the vulnerable AJAX endpoints

Patch Information

Organizations should check the official WordPress plugin repository for an updated version of the Invoct – PDF Invoices & Billing for WooCommerce plugin that addresses this vulnerability. The fix should implement proper capability checks using WordPress's current_user_can() function on all affected AJAX handlers. Monitor the Wordfence vulnerability report for patch availability announcements.

Workarounds

• Restrict the plugin's functionality to trusted administrators only by implementing custom capability checks via a security plugin
• Use a Web Application Firewall to block AJAX requests to the vulnerable endpoints from non-administrative users
• Limit user registration on the WordPress site to prevent attackers from easily obtaining authenticated sessions
• Consider using an alternative PDF invoice plugin until a patched version is available

# WordPress CLI command to check plugin version and deactivate if vulnerable
wp plugin list --name=kirilkirkov-pdf-invoice-manager --field=version
wp plugin deactivate kirilkirkov-pdf-invoice-manager