Online Scheduling and Appointment Booking System <= 28.2 - Insecure Direct Object Reference to Unauthenticated Arbitrary Booking Token Disclosure and Deletion via 'order_id' Parameter
Strategic Overview
- Status
- Patched in 28.3
- Affected Plugin
- Online Scheduling and Appointment Booking System – Bookly
- Affected Version
<= 28.2- CVSS
- 9.1Critical
- Weakness type
- CWE-639 · Authorization Bypass Through User-Controlled Key
- CVE
CVE-2026-93399
At a glance
CVE-2026-93399 is a critical-severity Authorization Bypass Through User-Controlled Key vulnerability in the Online Scheduling and Appointment Booking System WordPress plugin, affecting versions <= 28.2. It carries a CVSS score of 9.1 (reachable over the network; low attack complexity; high integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 28.3; sites on affected versions should update now. Disclosed September 2026, reported by Theklis.
Vulnerability Overview
The Bookly plugin for WordPress is vulnerable to Insecure Direct Object Reference in versions up to, and including, 28.2 via the 'bookly_get_form_id', 'bookly_render_complete', 'bookly_add_to_calendar' and 'bookly_rollback_order' AJAX actions. This is due to the 'bookly_get_form_id' handler blindly storing the attacker-controlled 'order_id' from the submitted form_data into a new booking session, which the 'bookly_render_complete' handler then trusts to look up and return the corresponding Order's secret token without verifying that the current session created that order. This makes it possible for unauthenticated attackers to enumerate sequential order IDs, disclose other customers' order tokens, retrieve calendar/appointment information via 'bookly_add_to_calendar' and permanently delete arbitrary non-completed bookings via 'bookly_rollback_order', which cascade-deletes the customer_appointment and (when no other customers are attached) the underlying appointment.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on integrity, availability.
CWE-639: Authorization Bypass Through User-Controlled Key
Online Scheduling and Appointment Booking System <= 28.2 carries this weakness at bookly_get_form_id, and reaching it takes no account at all. Authorization bypass through a user-controlled key, often called insecure direct object reference, means the application looks up a record by an identifier from the request without checking that the caller owns it.
Changing a number in the request is enough to read or modify other users' records, which on commerce and membership sites means customer data. For Online Scheduling and Appointment Booking System the fix is 28.3: builds <= 28.2 are affected, anything from 28.3 onward is not.
Remediation
Update to version 28.3, or a newer patched version
How does WordSec protect against this?
This one needs no account at all, which puts it outside what login hardening can reach; WordSec's login security narrows the account-level paths around it, and the firewall is what inspects the request itself. None of that substitutes for the fix: Online Scheduling and Appointment Booking System 28.3 closes this, and updating the plugin is the step that ends it.
- Login Security
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in Online Scheduling and Appointment Booking System – Bookly
- 8.1CVE-2023-26526: Bookly <= 21.7.1 Arbitrary File Deletion
CVE-2023-26526 - 7.5CVE-2026-13395: Online Scheduling and Appointment… SQL Injection
CVE-2026-13395 - 7.5CVE-2026-14516: Online Scheduling and Appointment… SQL Injection
CVE-2026-14516 - 7.5CVE-2026-61949: Online Scheduling and Appointment… SQL Injection
CVE-2026-61949 - 7.2CVE-2026-13424: Online Scheduling and Appointment… Stored XSS
CVE-2026-13424 - 7.2CVE-2026-61944: Online Scheduling and Appointment… Stored XSS
CVE-2026-61944 - 7.2CVE-2026-5513: Online Scheduling and Appointment… Stored XSS
CVE-2026-5513 - 7.2CVE-2023-1172: Bookly <= 21.5 Stored Cross-Site Scripting
CVE-2023-1172
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