The vulnerability identified as CVE-2025-3479 affects the Forminator Forms – Contact Form, Payment Form & Custom Form Builder plugin for WordPress, specifically versions up to 1.42.0. The root cause is an improper validation of an integrity check value (CWE-354) in the 'handle_stripe_single' function, which handles Stripe PaymentIntent objects. Attackers can exploit this flaw by replaying a previously used Stripe PaymentIntent, causing the plugin to accept multiple transactions based on a single payment authorization. Stripe itself processes only the first transaction, preventing multiple charges, but the plugin erroneously sends a successful transaction email for each replayed order. This discrepancy can deceive site administrators into believing multiple payments were made, leading to fraudulent order fulfillment or service delivery. The attack requires no authentication or user interaction and can be executed remotely over the network. The vulnerability has a CVSS 3.1 base score of 5.3, reflecting medium severity due to the lack of confidentiality or availability impact but a clear integrity impact. No patches or fixes have been published yet, and no known exploits have been detected in the wild. The issue highlights the importance of robust validation of payment-related data and integrity checks in e-commerce plugins to prevent replay and fraud attacks.

The primary impact of this vulnerability is financial fraud and operational disruption for organizations using the affected Forminator Forms plugin for payment processing. Attackers can cause the system to send multiple successful payment confirmations for a single Stripe PaymentIntent, tricking administrators into fulfilling multiple orders without receiving corresponding payments. This can lead to direct financial losses, inventory depletion, and reputational damage due to fraudulent transactions. Additionally, the administrative overhead to detect and remediate fraudulent orders can be significant. Since the vulnerability does not affect confidentiality or availability, data breaches or service outages are unlikely. However, the integrity of transaction processing is compromised, which is critical for e-commerce and payment systems. Organizations relying on this plugin, especially those with high transaction volumes or limited manual verification processes, are at increased risk. The lack of authentication or user interaction required for exploitation increases the attack surface and ease of abuse.

To mitigate this vulnerability, organizations should immediately audit their use of the Forminator Forms plugin and consider the following specific actions: 1) Temporarily disable payment processing via the Forminator plugin until a vendor patch is released. 2) Implement manual verification procedures for all payment confirmations received through the plugin to detect discrepancies between Stripe's actual processed payments and plugin-generated confirmations. 3) Monitor transaction logs for repeated use of the same Stripe PaymentIntent identifiers and flag suspicious activity. 4) Restrict access to the WordPress admin interface and form submission endpoints using web application firewalls (WAFs) and IP whitelisting to reduce exposure to unauthenticated attackers. 5) Engage with the plugin vendor (wpmudev) to obtain updates or patches addressing the integrity validation flaw as soon as they become available. 6) Consider alternative, more secure payment processing plugins or custom integrations that enforce strict validation of payment intents and confirmations. 7) Educate administrative staff about the potential for fraudulent order confirmations and establish procedures for cross-checking payment status directly with Stripe. These targeted measures go beyond generic advice by focusing on detection of replay attempts, restricting attack vectors, and compensating controls until a patch is available.