dbcve.org
Improper Input ValidationWeakness · CWE-20

CVE-2026-3641

MEDIUM · 5.3 CVSS v3.1 Published 2026-03-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Appmax WordPress plugin exposes a public REST API endpoint at /webhook-system that processes incoming webhook requests without any authentication. The endpoint accepts 'event' and 'data' parameters directly from unauthenticated requests, allowing attackers to manipulate WooCommerce order statuses, create fake orders/products, and write arbitrary metadata to existing orders. No signature validation, secret verification, or origin authentication exists.

MitigationImplement webhook signature validation using a shared secret between Appmax and the plugin, and add server-side validation of the 'event' and 'data' parameters before processing any WooCommerce data changes.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if Appmax plugin is installed
    Check the WordPress plugins directory for the Appmax plugin folder or query the wp_plugins database table for 'appmax' in the plugin name
    Affected if The Appmax plugin files exist in the WordPress installation
  2. Check if the plugin is active
    Query the wp_options table for the option_name 'active_plugins' and verify 'appmax' or 'appmax.php' is present in the serialized active plugins list
    Affected if The Appmax plugin appears in the list of active plugins
  3. Test for unauthenticated webhook endpoint exposure
    Send an unauthenticated HTTP GET or POST request to /wp-json/appmax/v1/webhook-system or /?rest_route=/appmax/v1/webhook-system and check for a non-401/non-403 response
    Affected if The endpoint returns a 200 OK response and accepts parameters without requiring authentication
  4. Inspect WooCommerce order modifications
    Review WooCommerce order logs in wp_postmeta and the wp_woocommerce_order_items table for unexpected status changes, new orders, or metadata writes with timestamps outside normal business operations
    Affected if Orders exist with status changes, creation timestamps, or metadata entries that were not initiated by known administrators or legitimate webhook sources
  5. Check for unknown webhook signatures in logs
    Examine server access logs and WordPress debug logs for POST requests to the webhook-system endpoint that lack the X-Appmax-Signature header or contain unexpected origin IPs
    Affected if Webhook requests are logged from unauthenticated sources or IPs that do not belong to the Appmax service infrastructure
  6. Review user roles with webhook permissions
    Query the wp_options table for any Appmax-related settings that may control which user roles or capabilities can configure webhook endpoints
    Affected if The plugin allows unauthenticated or low-privilege users to trigger order modifications without validation

A user is affected if the Appmax WordPress plugin is installed and active, and the /webhook-system endpoint accepts unauthenticated requests that can modify WooCommerce orders.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement webhook signature validation using a shared secret between Appmax and the plugin, and add server-side validation of the 'event' and 'data' parameters before processing any WooCommerce data changes.

Recommended fix Moderate confidence

Any version greater than 1.0.3 (check WordPress plugin repository for the latest stable release)

  1. 1. Log in to the WordPress admin dashboard
  2. 2. Navigate to Plugins > Installed Plugins
  3. 3. Locate the Appmax plugin in the list
  4. 4. If an update is available, click 'Update Now' to upgrade to the latest version (version greater than 1.0.3)
  5. 5. After updating, verify the plugin version in the plugins list to confirm the update was successful
  6. 6. Review the plugin settings to ensure webhook signature validation or authentication is now properly configured if required

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-3641 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data