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The Fluent Forms Pro Add On Pack plugin for WordPress is...

High severity Unreviewed Published Feb 27, 2026 to the GitHub Advisory Database • Updated Feb 27, 2026

Package

No package listed— Suggest a package

Affected versions

Unknown

Patched versions

Unknown

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

Published by the National Vulnerability Database Feb 27, 2026
Published to the GitHub Advisory Database Feb 27, 2026
Last updated Feb 27, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(10th percentile)

Weaknesses

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Learn more on MITRE.

CVE ID

CVE-2026-2428

GHSA ID

GHSA-23j5-87fx-hgc9

Source code

No known source code

Dependabot alerts are not supported on this advisory because it does not have a package from a supported ecosystem with an affected and fixed version.

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