CVE-2025-12788 is a vulnerability classified under CWE-602 (Client-Side Enforcement of Server-Side Security) found in the Hydra Booking — Appointment Scheduling & Booking Calendar plugin for WordPress. The vulnerability exists because the plugin's function tfhb_meeting_paypal_payment_confirmation_callback accepts payment confirmation data directly from the client without verifying it server-side with PayPal's API. This design flaw allows unauthenticated attackers to craft requests that falsely indicate payment completion, thereby bypassing payment requirements and confirming bookings as paid without any actual transaction. The vulnerability affects all plugin versions up to and including 1.1.27. Exploitation requires no authentication or user interaction and can be performed remotely over the network. The CVSS v3.1 base score is 5.3 (medium), reflecting the lack of confidentiality or availability impact but a clear integrity impact due to unauthorized booking confirmation. No patches or official fixes are currently linked, and no known exploits have been reported in the wild. The vulnerability poses a risk to organizations relying on this plugin for appointment scheduling and payment processing, potentially leading to revenue loss, fraudulent bookings, and reputational damage.

For European organizations using the Hydra Booking plugin, this vulnerability can result in unauthorized free bookings, leading to direct financial losses and potential operational disruptions. Businesses such as clinics, salons, consultancy services, and other appointment-based services that rely on this plugin for payment processing may experience revenue leakage. Additionally, fraudulent bookings can cause scheduling conflicts, resource misallocation, and customer dissatisfaction. The integrity of the booking system is compromised, which may erode trust in the service provider. While the vulnerability does not directly impact confidentiality or availability, the indirect effects on business operations and customer trust can be significant. Given the widespread use of WordPress and e-commerce in Europe, the threat is relevant to many small and medium enterprises. The lack of authentication or user interaction required for exploitation increases the risk of automated abuse or mass exploitation attempts.

1. Implement server-side payment verification by integrating PayPal's API to validate payment confirmations before marking bookings as paid. 2. Update the Hydra Booking plugin to a patched version once available; monitor vendor announcements for fixes. 3. In the interim, restrict access to the payment confirmation callback endpoint using web application firewalls (WAF) or IP whitelisting to limit exposure. 4. Monitor booking records for anomalies such as unusually high numbers of paid bookings without corresponding PayPal transactions. 5. Employ rate limiting on the payment confirmation endpoint to reduce automated exploitation attempts. 6. Consider disabling the plugin or switching to alternative booking solutions with robust payment verification if patching is not immediately possible. 7. Educate staff to verify payments manually when suspicious bookings are detected. 8. Regularly audit and update WordPress plugins to minimize exposure to known vulnerabilities.