CVE-2026-2428 is a vulnerability classified under CWE-345 (Insufficient Verification of Data Authenticity) found in the Fluent Forms Pro Add On Pack plugin for WordPress. The root cause is that the PayPal Instant Payment Notification (IPN) verification mechanism is disabled by default (`disable_ipn_verification` is set to 'yes' in the PayPalSettings.php file). This design flaw allows unauthenticated attackers to send forged IPN messages to the plugin's publicly accessible IPN endpoint. Because the plugin trusts these forged notifications without verifying their authenticity with PayPal, it can incorrectly mark unpaid form submissions as paid. This triggers automated workflows such as sending confirmation emails, granting access to restricted content, or delivering digital products. The vulnerability affects all versions up to and including 6.1.17. The CVSS v3.1 score is 7.5 (high), reflecting the ease of exploitation (network vector, no privileges or user interaction required) and the significant impact on data integrity. No known exploits are reported in the wild yet. The vulnerability compromises the integrity of payment processing but does not affect confidentiality or availability. This flaw can lead to financial losses and unauthorized access to paid services or products. The vulnerability is particularly critical for organizations relying on this plugin for e-commerce or subscription management on WordPress sites.

The primary impact of CVE-2026-2428 is the potential for financial fraud and unauthorized access to paid digital goods or services. Attackers can exploit this vulnerability to bypass payment verification, causing the system to treat unpaid transactions as completed. This undermines the integrity of payment processing and can result in revenue loss for businesses. Additionally, automated post-payment actions such as granting access to premium content, sending confirmation emails, or delivering digital products can be triggered fraudulently, leading to unauthorized resource access and potential reputational damage. Organizations using this plugin in their WordPress environments, especially those handling significant volumes of online payments, are at risk. The vulnerability does not directly affect confidentiality or availability but can indirectly cause operational disruptions due to fraudulent transactions and customer disputes. The ease of exploitation and lack of required authentication increase the threat level globally, particularly for e-commerce, digital content providers, and subscription-based services.

To mitigate CVE-2026-2428, organizations should immediately verify and ensure that PayPal IPN verification is enabled in the Fluent Forms Pro Add On Pack plugin configuration. Specifically, the `disable_ipn_verification` setting in PayPalSettings.php must be set to 'no' to enforce IPN message authenticity checks. If a patch or updated plugin version is released by techjewel, it should be applied promptly. Additionally, organizations should implement server-side logging and monitoring of IPN endpoint activity to detect suspicious or anomalous payment notifications. Employing web application firewalls (WAFs) with rules to validate IPN traffic or block suspicious requests can provide an additional layer of defense. It is also advisable to conduct regular audits of payment records to identify discrepancies between payment gateway records and internal transaction statuses. For critical environments, consider implementing multi-factor verification of payment status before triggering automated post-payment workflows. Finally, educating site administrators about this vulnerability and encouraging timely updates and configuration reviews will reduce exposure.