Appmax <= 1.0.3 - Missing Authorization to Order Status Manipulation and Arbitrary Order Creation via Webhook Endpoint
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- Appmax
- Affected Version
<= 1.0.3- CVSS
- 5.3Medium
- Weakness type
- CWE-20 · Improper Input Validation
- CVE
CVE-2026-3641
At a glance
CVE-2026-3641 is a medium-severity Improper Input Validation vulnerability in the Appmax WordPress plugin, affecting versions <= 1.0.3. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed March 2026, reported by chaeyp.
Vulnerability Overview
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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user.
CWE-20: Improper Input Validation
Appmax <= 1.0.3 carries this weakness at event, and reaching it takes a caller who can reach the endpoint. Improper input validation means the application accepts input without confirming it has the form, type or range the code downstream assumes.
The concrete impact depends on where the unvalidated value lands, which is why records in this class range from cosmetic bugs to full compromise. No fixed build of this plugin is recorded for Appmax yet, so installs running <= 1.0.3 stay exposed until the vendor ships one.
Remediation
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.
How does WordSec protect against this?
The attempt arrives as an ordinary request to Appmax: WordSec's web application firewall inspects request payloads before WordPress loads them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C