CVE-2026-4160

Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder <= 6.1.21 - Insecure Direct Object Reference in Stripe SCA Confirmation to Unauthenticated Payment Status Modification

2026-04-16 00:53
Prickly Cactus

Strategic Overview

Status
Patched in 6.2.0
Affected Plugin
Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder
Affected Version
6.1.21
CVSS
5.3Medium
Weakness type
CWE-639 · Authorization Bypass Through User-Controlled Key
CVE
CVE-2026-4160
View all Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder vulnerabilities

At a glance

CVE-2026-4160 is a medium-severity Authorization Bypass Through User-Controlled Key vulnerability in the Fluent Forms WordPress plugin, affecting versions 6.1.21. It carries a CVSS score of 5.3 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 6.2.0; sites on affected versions should update now. Disclosed April 2026, reported by Prickly Cactus.

Vulnerability Overview

The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to Insecure Direct Object Reference via the 'submission_id' parameter in versions up to, and including, 6.1.21. This is due to missing authorization and ownership validation on a user controlled key in the Stripe SCA confirmation AJAX endpoint. This makes it possible for unauthenticated attackers to modify payment status of targeted pending submissions (for example, setting the status to "failed").

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-639: Authorization Bypass Through User-Controlled Key

Fluent Forms 6.1.21 carries this weakness at submission_id, and reaching it takes no account at all. Authorization bypass through a user-controlled key, often called insecure direct object reference, means the application looks up a record by an identifier from the request without checking that the caller owns it.

Changing a number in the request is enough to read or modify other users' records, which on commerce and membership sites means customer data. For Fluent Forms the fix is 6.2.0: builds 6.1.21 are affected, anything from 6.2.0 onward is not.

Remediation

Update to version 6.2.0, or a newer patched version

How does WordSec protect against this?

This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: Fluent Forms 6.2.0 closes this, and updating the plugin is the step that ends it.

  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-4160https://www.wordfence.com/threat-intel/vulnerabilities/id/154fc656-3a33-4783-a941-10bb848244b3https://nvd.nist.gov/vuln/detail/CVE-2026-4160

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C