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Vulnerability record · CVE-2026-2428 · published 27 February 2026

CVE-2026-2428: Insufficient verification of data authenticity vulnerability

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).

7.5 CVSS 3.1 High EPSS 0.14% · top 97.1% CWE-345 · Insufficient verification of data authenticity Deferred
7.5CVSS 3.1 base score
0.14%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

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).

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

LinkTags
https://fluentforms.com/docs/changelog/#2-toc-title
https://www.wordfence.com/threat-intel/vulnerabilities/id/e5c62e54-da06-4b44-ba70-63065e664b0d?source=cve

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Source: NIST National Vulnerability Database (record CVE-2026-2428), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.