CVE-2025-12788 Overview
CVE-2025-12788 affects the Hydra Booking — Appointment Scheduling & Booking Calendar plugin for WordPress. The plugin fails to verify PayPal payment confirmations server-side, trusting client-supplied data instead. All versions up to and including 1.1.27 are vulnerable. Unauthenticated attackers can bypass payment requirements and mark bookings as paid without completing an actual PayPal transaction. The flaw resides in the tfhb_meeting_paypal_payment_confirmation_callback function, which accepts client-controlled confirmation data without calling PayPal's API for validation. This vulnerability is classified under [CWE-602] Client-Side Enforcement of Server-Side Security.
Critical Impact
Unauthenticated attackers can confirm paid bookings on affected WordPress sites without processing any real payment, resulting in direct revenue loss for site operators.
Affected Products
- Hydra Booking — Appointment Scheduling & Booking Calendar plugin for WordPress
- All versions up to and including 1.1.27
- Fixed in version 1.1.28
Discovery Timeline
- 2025-11-11 - CVE-2025-12788 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-12788
Vulnerability Analysis
The vulnerability is a business logic flaw in the PayPal payment integration of Hydra Booking. When a user initiates a booking that requires payment, the plugin exposes an AJAX endpoint that handles the PayPal payment confirmation callback. This endpoint, implemented in tfhb_meeting_paypal_payment_confirmation_callback, accepts payment status data supplied directly by the client browser. The plugin then updates the booking status to paid based on that input alone. No out-of-band verification is performed against PayPal's Orders or Payments API to confirm that the referenced transaction actually exists, was captured, and matches the expected amount and payee.
Root Cause
The root cause is a violation of the principle that security decisions must be enforced server-side. The plugin treats client-submitted parameters such as payment identifiers and status flags as authoritative. Because these values traverse the user's browser, an attacker can arbitrarily set them. The fix in version 1.1.28 modifies the HydraBookingShortcode.php shortcode handler to enforce server-side verification of the PayPal transaction before confirming the booking.
Attack Vector
An unauthenticated attacker submits a crafted HTTP request to the vulnerable callback endpoint. The request contains fabricated PayPal transaction metadata indicating a successful payment. The plugin processes the input and marks the corresponding booking as paid without contacting PayPal. The attacker receives a confirmed reservation while the site operator receives no funds.
See the Wordfence Vulnerability Report and the WordPress Plugin Change Log for full technical details.
Detection Methods for CVE-2025-12788
Indicators of Compromise
- Booking records marked as paid in the Hydra Booking database that lack matching transactions in the site's PayPal merchant account.
- Unusual volumes of successful bookings originating from a small set of source IP addresses.
- HTTP requests to admin-ajax endpoints referencing the tfhb_meeting_paypal_payment_confirmation_callback action with anomalous or repeated payload structures.
Detection Strategies
- Reconcile confirmed booking records against actual PayPal transaction reports on a scheduled basis.
- Inspect web server access logs for POST requests to admin-ajax.php invoking the vulnerable PayPal callback action.
- Alert on bookings where the recorded PayPal transaction identifier does not appear in PayPal's API when queried directly.
Monitoring Recommendations
- Enable verbose logging on the WordPress site and forward logs to a centralized platform for retrospective analysis.
- Monitor for spikes in booking creation immediately followed by paid-status transitions with no corresponding payment gateway callback in outbound network traffic.
- Track the installed version of the Hydra Booking plugin across all managed WordPress instances until upgraded to 1.1.28 or later.
How to Mitigate CVE-2025-12788
Immediate Actions Required
- Update the Hydra Booking plugin to version 1.1.28 or later on every WordPress site where it is installed.
- Audit all bookings created while running versions 1.1.27 and earlier to identify fraudulent paid confirmations.
- Reconcile plugin booking records against PayPal merchant transaction history and cancel unmatched bookings.
Patch Information
The vendor released version 1.1.28 of Hydra Booking to address CVE-2025-12788. The patch modifies app/Shortcode/HydraBookingShortcode.php to introduce server-side verification with PayPal's API before confirming a booking as paid. Review the changeset in the WordPress Plugin Change Log for implementation specifics.
Workarounds
- If immediate upgrade is not possible, disable the Hydra Booking plugin until the update can be applied.
- Temporarily disable PayPal as an available payment method within the plugin configuration to prevent abuse of the vulnerable callback.
- Restrict access to the WordPress admin-ajax.php endpoint using a web application firewall rule that blocks unauthenticated requests referencing the tfhb_meeting_paypal_payment_confirmation_callback action.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
