CVE-2026-18328 Forminator Forms <= 1.57.0 - Unauthenticated DOM-Based Cross-Site Scripting via 'error_description' Parameter
Unauthenticated attackers can inject arbitrary scripts via the error_description parameter in Forminator Forms, affecting sites using Stripe Checkout Sessions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-18328?
CVE-2026-18328 is a high-severity cross-site scripting vulnerability in wpmudev Forminator Forms – Contact Form, Payment Form & Custom Form Builder, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The Forminator Forms – Contact Form, Payment Form & Custom Form Builder plugin for WordPress is vulnerable to DOM-Based Reflected Cross-Site Scripting via the 'error_description' parameter in all versions up to, and including, 1.57.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The vulnerability is only triggerable on pages hosting a Forminator form configured to use the Stripe Checkout Sessions payment API, which became the default in 1.56.0.
Weakness: CWE-79
Which versions are affected by CVE-2026-18328?
How do I fix CVE-2026-18328?
No fix has been published for CVE-2026-18328 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-18328 being exploited?
There is no known exploitation of CVE-2026-18328 in the wild and no public exploit code.
Sources
Also known as GHSA-5mm9-h6w4-7v8m.