Fluent Forms Pro Add On Pack <= 6.1.17 - Missing Authorization to Unauthenticated Payment Status modification

Insufficient Verification of Data Authenticity
CVE CVE-2026-2428
CVSS High (7.5)
Publicly Published February 26, 2026
Last Updated February 27, 2026
Researcher Prickly Cactus
Description

The Fluent Forms Pro Add On Pack plugin for WordPress is vulnerable to Insufficient Verification of Data Authenticity in all versions up to, and including, 6.1.17. This is due to the PayPal IPN (Instant Payment Notification) verification being disabled by default (`disable_ipn_verification` defaults to `'yes'` in `PayPalSettings.php`). This makes it possible for unauthenticated attackers to send forged PayPal IPN notifications to the publicly accessible IPN endpoint, marking unpaid form submissions as "paid" and triggering post-payment automation (emails, access grants, digital product delivery).

References

1 affected software package

Software Type Plugin
Software Slug fluentformpro (view on wordpress.org)
Patched? Yes
Affected Version
  • <= 6.1.17
Patched Version
  • 6.1.18
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