CVE-2026-18146

Fluent Forms <= 6.2.11 - Unauthenticated Stored Cross-Site Scripting via Notification Smartcode Values

2026-08-12 18:34
Adrien Brunner

Strategic Overview

Status
Patched in 6.2.12
Affected Plugin
Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder
Affected Version
<= 6.2.11
CVSS
7.2High
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-18146
View all Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder vulnerabilities

At a glance

CVE-2026-18146 is a high-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Fluent Forms WordPress plugin, affecting versions <= 6.2.11. It carries a CVSS score of 7.2 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 6.2.12; sites on affected versions should update now. Disclosed August 2026, reported by Adrien Brunner.

Vulnerability Overview

The Fluent Forms – Customizable Contact Forms, Survey, Quiz, & Conversational Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Notification Smartcode Values in all versions up to, and including, 6.2.11 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that execute in the browser of an administrator (or any user with the Fluent Forms entry-viewing capability) when they view the form's entry Submission Logs in the WordPress admin dashboard. Exploitation requires that a site administrator or Fluent Forms manager has configured an email notification whose subject or static (direct) Send To value references an attacker-influenced Smartcode such as an input_password field value, a cookie value, or submission.response.

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-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in Fluent Forms <= 6.2.11 takes no account at all. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Fluent Forms the fix is 6.2.12: builds <= 6.2.11 are affected, anything from 6.2.12 onward is not.

Remediation

Update to version 6.2.12, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Fluent Forms 6.2.12 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-18146https://www.wordfence.com/threat-intel/vulnerabilities/id/643f92e2-b14e-4056-97fc-1c631027c54fhttps://nvd.nist.gov/vuln/detail/CVE-2026-18146

Related records

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