Auth bypass in Strategy11team Formidable Forms – Contact Form Plugin, Survey, Quiz, Payment, Calculator & Custom Builder

CVE-2026-2890

The Formidable Forms plugin for WordPress is vulnerable to a payment integrity bypass in all versions up to, and including, 6.28. This is due to the Stripe Link return handler (`handle_one_time_stripe_link_return_url`) marking payment records as complete based solely on the Stripe PaymentIntent status without comparing the intent's charged amount against the expected payment amount, and the `verify_intent()` function validating only client secret ownership without binding intents to specific forms or actions. This makes it possible for unauthenticated attackers to reuse a PaymentIntent from a completed low-value payment to mark a high-value payment as complete, effectively bypassing payment for goods or services.

Vulnerability class: Broken Access Control

EPSS: 0.003 (23.2th percentile) — read the EPSS interpretation.