CVE-2026-27377 in QuickCal Plugin
Summary
by MITRE • 07/23/2026
Booking Agent Broken Access Control in QuickCal - Appointment Booking Calendar for WordPress <= 1.0.16 versions.
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Analysis
by VulDB Data Team • 07/23/2026
The QuickCal appointment booking calendar for WordPress plugin presents a critical broken access control vulnerability that allows unauthorized users to manipulate booking data through improper authorization checks. This vulnerability affects versions 1.0.16 and earlier, where the plugin fails to properly validate user permissions when processing booking requests. The flaw stems from insufficient input validation and inadequate privilege verification mechanisms within the plugin's core functionality, particularly in how it handles appointment scheduling and modification operations.
The technical implementation of this vulnerability resides in the plugin's backend processing logic where booking-related endpoints do not adequately verify whether the requesting user possesses appropriate authorization levels to perform specific actions. Attackers can exploit this weakness by crafting malicious requests that bypass normal access controls, potentially enabling them to view, modify, or delete appointments without proper authentication. The vulnerability manifests when the system fails to distinguish between legitimate users and unauthorized parties during booking operations, creating a path for privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple data exposure, as it can lead to complete compromise of the booking calendar system. An attacker with minimal privileges could potentially access sensitive customer information including personal details, contact information, and scheduling preferences stored within the appointment database. This breach of access control can result in service disruption, data loss, and potential regulatory violations depending on the nature of the booked services and customer data involved.
Security professionals should implement immediate mitigations including updating to the latest plugin version where this vulnerability has been patched, implementing additional authentication layers, and conducting thorough access control reviews. The vulnerability aligns with CWE-285 which specifically addresses improper authorization issues, and maps to ATT&CK technique T1078 for valid accounts and privilege escalation. Organizations should also consider deploying web application firewalls to monitor and block suspicious booking-related requests, while establishing proper monitoring of user activities within the calendar system to detect potential exploitation attempts.