CVE-2026-89063
HighOnline Scheduling and Appointment Booking System <= 28.1 - Insecure Direct Object Reference to Unauthenticated Sensitive Data Access and Message Injection via 'conversation_id' Parameter
Published Sep 15, 2026 · Updated Sep 17, 2026 · Also known as EUVD-2026-80112, GHSA-f895-wc4g-97xv, b6af015f-f954-4afb-9d65-56176f73672f
Key Facts
Patch in the next maintenance window- CVE-2026-89063 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting bookly-responsive-appointment-booking-tool (wordpress-plugin), Online Scheduling and Appointment Booking System – Bookly.
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 1.6% probability of exploitation in the next 30 days.
- Fixed versions are available, including bookly-responsive-appointment-booking-tool 28.2.
- Brandefense priority: patch in the next maintenance window, because of its high severity, although no exploitation is known.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (30-day exploit likelihood)
1.6%
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2026-89063 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
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.
Affected Products
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| bookly-responsive-appointment-booking-toolwordpress-plugin | See advisory | 28.2 |
| Online Scheduling and Appointment Booking System – Bookly | See advisory | n/a |
Patched Releases
bookly-responsive-appointment-booking-tool
28.2
Timeline
Publicly disclosed
Sep 15, 2026
Last updated
Sep 17, 2026
Weakness Type
- CWE-639 Authorization Bypass Through User-Controlled Key
References
- advisoryhttps://patchstack.com/database
- advisoryhttps://wpscan.com/plugins/
- advisoryUSOM advisory
- advisoryhttps://www.wordfence.com/threat-intel/vulnerabilities/
- advisoryhttps://www.wordfence.com/threat-intel/vulnerabilities/id/b6af015f-f954-4afb-9d65-56176f73672f?source=api-prod
FAQ
Common Questions.
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.
Affected: bookly-responsive-appointment-booking-tool (wordpress-plugin); Online Scheduling and Appointment Booking System – Bookly. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including bookly-responsive-appointment-booking-tool 28.2.
Brandefense priority: patch in the next maintenance window, because of its high severity, although no exploitation is known.
Is CVE-2026-89063 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo