Description

The Quick Event Manager WordPress plugin before 9.19 does not verify the authenticity of PayPal payment notifications before marking event registrations as paid, which could allow unauthenticated attackers to mark registrations as paid without making a payment.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.3",
  "pubDate": "2026-11-06T08:17:20.103Z",
  "pubdate": "2026-11-06T08:17:20.103Z",
  "executiveSummary": "The Quick Event Manager WordPress plugin, in versions prior to 9.19, contains a critical vulnerability related to the improper verification of payment notifications. The flaw stems from a failure to validate the authenticity of incoming PayPal IPN (Instant Payment Notification) requests before updating the status of event registrations within the database.\nThis vulnerability allows unauthenticated remote attackers to bypass the payment gateway entirely, forcing the application to mark pending event registrations as 'paid' without any actual financial transaction occurring. The impact of this security deficiency is significant, as it permits unauthorized access to event-related benefits, undermines the plugin's revenue management capabilities, and leads to potential service abuse.\nThe vulnerability requires no authentication and is accessible via the network, making it a high-risk security issue for WordPress sites utilizing this plugin for event management and ticketing. Attackers can simulate successful PayPal notifications through crafted HTTP requests to the target, deceiving the server into modifying registration records. There are no special privileges required to trigger this logic, provided the attacker can reach the endpoint responsible for processing these notifications.",
  "technicalDetails": "The root cause of this vulnerability lies in the insufficient server-side validation of PayPal IPN messages. In the affected versions of the Quick Event Manager plugin, the logic responsible for handling payment status updates fails to communicate back with the PayPal API to verify the integrity and origin of the received data.\nWhen a user or a third party triggers the event registration process, the plugin expects a callback from the payment provider to confirm the transaction status. An attacker can exploit this by crafting a POST request containing forged payment parameters that mimic the structure of a legitimate PayPal notification. Because the plugin does not perform a secondary validation step—such as sending a request back to PayPal to confirm the transaction ID (txn_id) or validating the notification origin via the PayPal IPN listener verification process—it blindly accepts the attacker-provided data as authentic.\nThe attack flow proceeds as follows: First, the attacker identifies the public-facing endpoint configured to receive payment notifications. Second, the attacker constructs a malicious payload containing the necessary fields, such as 'payment_status=Completed' and relevant registration IDs, which the plugin's backend relies upon to perform database updates. Third, the attacker transmits this payload directly to the notification listener. Upon receipt, the plugin parses these parameters and immediately updates the corresponding registration record in the WordPress database to a paid status without verifying that the transaction was actually initiated or finalized by the service provider.\nThis behavior results in unauthorized privilege elevation regarding event access, as the system effectively treats the unauthenticated request as a verified confirmation of payment. The vulnerability persists across all versions prior to 9.19. Post-exploitation, the attacker may gain access to private event details, tickets, or registration perks intended only for paying attendees, while simultaneously causing financial loss and data integrity issues for the site administrator. The lack of cryptographic signature checking or source IP validation on the incoming requests ensures that this manipulation remains trivial to execute for any remote actor capable of reaching the web server."
}