CVE-2026-89063

Online Scheduling and Appointment Booking System <= 28.1 - Insecure Direct Object Reference to Unauthenticated Sensitive Data Access and Message Injection via 'conversation_id' Parameter

2026-09-15 15:39
jtb75

Strategic Overview

Status
Patched in 28.2
Affected Version
<= 28.1
CVSS
7.5High
Weakness type
CWE-639 · Authorization Bypass Through User-Controlled Key
CVE
CVE-2026-89063
View all Online Scheduling and Appointment Booking System – Bookly vulnerabilities

At a glance

CVE-2026-89063 is a high-severity Authorization Bypass Through User-Controlled Key vulnerability in the Online Scheduling and Appointment Booking System WordPress plugin, affecting versions <= 28.1. It carries a CVSS score of 7.5 (reachable over the network; low attack complexity; high confidentiality impact). Exploitation requires no authentication. The issue is fixed in version 28.2; sites on affected versions should update now. Disclosed September 2026, reported by jtb75.

Vulnerability Overview

The Online Scheduling and Appointment Booking System – Bookly plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 28.1 via the 'conversation_id' parameter due to missing validation on a user controlled key. This makes it possible for unauthenticated attackers to read the full AI booking conversation transcript of any customer — leaking names, email addresses, phone numbers, and appointment details echoed by the assistant — and inject arbitrary messages into any victim conversation that are subsequently replayed to the Cloud AI worker along with the full private history. Because AI conversations are stored with no owner, user, or session identifier and conversation IDs are sequential integers, an unauthenticated attacker can enumerate all customer conversations simply by incrementing the conversation_id parameter.

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 confidentiality.

CWE-639: Authorization Bypass Through User-Controlled Key

Online Scheduling and Appointment Booking System <= 28.1 carries this weakness at conversation_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 28.2: builds <= 28.1 are affected, anything from 28.2 onward is not.

Remediation

Update to version 28.2, 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 28.2 closes this, and updating the plugin is the step that ends it.

  • Login Security
  • Alerts

External References

Related records

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