Appmax <= 1.0.3 — Missing Authorization to Order Status Manipulation and Arbitrary Order Creation via Webhook Endpoint

Am I affected?

• Check your version: in wp-admin go to Plugins → Installed Plugins and read the version under Appmax.
• No admin access? Run a passive check of your site. It reads public files only.
• No account is needed to exploit this. Treat any exposed site on an affected version as at risk.

What to do

1. No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
2. Rotate administrator passwords and application secrets if the site ran a vulnerable version while publicly reachable.
3. Watch Appmax to get an email when the next vulnerability is published.

Advisory

Source description from Wordfence Intelligence, credited to chaeyp, Ronnachai Sretawat Na Ayutaya (Simonhaskelly), Ronnachai Chaipha (rxnr).

The Appmax plugin for WordPress is vulnerable to Improper Input Validation in all versions up to, and including, 1.0.3. This is due to the plugin registering a public REST API webhook endpoint at /webhook-system without implementing webhook signature validation, secret verification, or any mechanism to authenticate that incoming webhook requests genuinely originate from the legitimate Appmax payment service. The plugin directly processes untrusted attacker-controlled input from the 'event' and 'data' parameters without verifying the webhook's authenticity. This makes it possible for unauthenticated attackers to craft malicious webhook payloads that can modify the status of existing WooCommerce orders (e.g., changing them to processing, refunded, cancelled, or pending), create entirely new WooCommerce orders with arbitrary data, create new WooCommerce products with attacker-controlled names/descriptions/prices, and write arbitrary values to order post metadata by spoofing legitimate webhook events.

Exploits & references

Proof-of-concept & detection

No public proof-of-concept or detection template is known for this vulnerability.

Advisories & patches

• Advisorywordfence.com

Timeline

1. Mar 20, 2026

   CVE published

   Severity medium, CVSS 5.3

2. Nov 13, 2026

   Record last updated