CVE-2025-13384 is a Missing Authorization vulnerability (CWE-862) affecting the CP Contact Form with PayPal WordPress plugin in all versions up to and including 1.3.56. The vulnerability stems from the plugin exposing an unauthenticated endpoint triggered via the 'cp_contactformpp_ipncheck' query parameter. This endpoint mimics PayPal's Instant Payment Notification (IPN) mechanism but lacks any authentication, nonce verification, or signature validation to confirm the legitimacy of incoming payment confirmation requests. As a result, an attacker can send arbitrary POST requests containing forged payment data such as payment_status, txn_id, and payer_email to this endpoint. The plugin then processes these forged notifications as valid payments, marking form submissions as paid without any actual transaction occurring. This flaw allows attackers to bypass payment requirements, potentially enabling fraudulent access to goods, services, or digital content. The vulnerability is remotely exploitable without any user interaction or authentication, increasing its risk profile. Despite the high CVSS score of 7.5, no patches or fixes have been published at the time of disclosure, and no known exploits have been observed in the wild. The vulnerability impacts the integrity of payment processing and could lead to financial losses and trust erosion for affected sites.

For European organizations, particularly those operating e-commerce platforms, donation portals, or any service relying on the CP Contact Form with PayPal plugin, this vulnerability poses a significant risk of financial fraud. Attackers can exploit the flaw to falsely mark payments as completed, granting unauthorized access to products or services without payment. This can result in direct revenue loss, increased chargebacks, and administrative overhead to reconcile fraudulent transactions. Additionally, the integrity of transaction records is compromised, which may affect accounting and compliance efforts. Organizations may suffer reputational damage if customers or partners perceive their payment systems as insecure. Given the plugin's integration with PayPal, a widely used payment method in Europe, the vulnerability could disrupt trust in online payment workflows. The lack of authentication and signature verification means the attack surface is broad, and exploitation can be automated at scale. This threat is particularly critical for small to medium enterprises that may lack robust monitoring or incident response capabilities.

Immediate mitigation steps include disabling the CP Contact Form with PayPal plugin until a security patch is available. If disabling is not feasible, restrict access to the vulnerable endpoint by implementing web application firewall (WAF) rules that block requests containing the 'cp_contactformpp_ipncheck' query parameter from untrusted IP addresses. Organizations should also implement server-side validation of IPN messages by verifying PayPal's IPN signatures or using PayPal's official IPN verification endpoints to ensure authenticity. Monitoring and logging all payment-related requests for anomalies such as repeated or suspicious payment_status values and txn_id reuse can help detect exploitation attempts. Updating the plugin to a patched version once released is critical. Additionally, organizations should review their payment reconciliation processes to identify and remediate any fraudulent transactions resulting from this vulnerability. Educating site administrators about the risks and signs of exploitation can improve detection and response times.