CVE-2026-13358

Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin <= 1.6.12.10 - Authenticated (Contributor+) Insecure Direct Object Reference to Sensitive Information Exposure

2026-08-15 15:27
Michael Iden (Mickhat)

Strategic Overview

Status
Patched in 1.6.12.11
Affected Version
<= 1.6.12.10
CVSS
6.5Medium
Weakness type
CWE-639 · Authorization Bypass Through User-Controlled Key
CVE
CVE-2026-13358
View all Simply Schedule Appointments vulnerabilities

At a glance

CVE-2026-13358 is a medium-severity Authorization Bypass Through User-Controlled Key vulnerability in the Simply Schedule Appointments WordPress plugin, affecting versions <= 1.6.12.10. It carries a CVSS score of 6.5 (reachable over the network; low attack complexity; high confidentiality impact). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 1.6.12.11; sites on affected versions should update now. Disclosed August 2026, reported by Michael Iden (Mickhat).

Vulnerability Overview

The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.6.12.10 via the ssa_past_appointments due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with contributor-level access and above, to access appointment records belonging to arbitrary users and harvest the per-appointment ownership tokens (32-character hashes) embedded in the rendered HTML, which can then be used without any authentication to read or modify those appointments including full customer PII such as name, email, phone number, and private notes. The /wp-json/ssa/v1/render-shortcode REST endpoint is registered unconditionally on rest_api_init regardless of whether the Divi theme is installed, and its permission callback only requires current_user_can('edit_posts'), meaning any Contributor-level account is sufficient to trigger this entire exploit chain.

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 interaction from a victim user. A successful exploit has high impact on confidentiality.

CWE-639: Authorization Bypass Through User-Controlled Key

Simply Schedule Appointments <= 1.6.12.10 carries this weakness at edit_posts, and reaching it takes an account at Contributor level or above. 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 Simply Schedule Appointments the fix is 1.6.12.11: builds <= 1.6.12.10 are affected, anything from 1.6.12.11 onward is not.

Remediation

Update to version 1.6.12.11, or a newer patched version

How does WordSec protect against this?

Because it turns on account access, WordSec's login security is the relevant layer: role-based two-factor, captcha and brute-force limits raise the cost of getting the account this needs. None of that substitutes for the fix: Simply Schedule Appointments 1.6.12.11 closes this, and updating the plugin is the step that ends it.

  • Login Security
  • Alerts

External References

Related records

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