Summary
CVE-2026-16142 is a critical unauthenticated account takeover vulnerability in the TrueBooker – Appointment Booking and Scheduler System WordPress plugin, affecting all versions up to and including 1.2.6. The flaw stems from an authorization bypass (CWE-639) that allows an attacker to change the email address of any WordPress user, including administrators, and then leverage the standard password-reset flow to seize the account. The vulnerability carries a CVSS v3.1 base score of 9.8 (Critical).
Technical details
- Root cause: the plugin’s
add_front_user_update()AJAX handler accepts an attacker-suppliedtruebooker_wp_user_idparameter and passes it directly to WordPress’swp_update_user()function without verifying the requester is authorized to modify that user. - Trigger conditions: the AJAX action is reachable by unauthenticated visitors; no login, nonce validation tied to the target user, or capability check is enforced.
- Attack vector: network-based, requires no user interaction and no prior authentication (AV:N/AC:L/PR:N/UI:N).
- Impact: an attacker can overwrite the email address on any account (including administrators), then trigger WordPress’s built-in password reset to receive the reset link at an attacker-controlled address, resulting in full account takeover and complete loss of confidentiality, integrity, and availability of the site.
Affected software
- TrueBooker – Appointment Booking and Scheduler System (WordPress plugin) — versions up to and including 1.2.6
Severity
- CVSS v3.1 Base Score: 9.8 (Critical)
- Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Mitigation and recommended actions
- Immediate: Update the TrueBooker – Appointment Booking and Scheduler System plugin to a version newer than 1.2.6 as soon as the vendor releases a fix; confirm the changelog explicitly addresses the
truebooker_wp_user_id/add_front_user_update()authorization issue before considering the site remediated. - If no patch is yet available: disable or remove the TrueBooker plugin until a fixed version is confirmed, restrict access to
wp-admin/admin-ajax.phpactions related to the plugin at the web server or WAF layer, and monitor administrator account email addresses for unauthorized changes.
How IONIX identifies potentially affected assets
IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.
- Raw response body:
/wp-content/plugins/truebooker-appointment-booking/

