CVE-2026-13424

Online Scheduling and Appointment Booking System <= 27.7 - Unauthenticated Stored Cross-Site Scripting via bookly_speed_up_update_addons AJAX action

2026-08-15 17:53
Dmitrii Ignatyev

Strategic Overview

Status
Patched in 28.0
Affected Plugin
Online Scheduling and Appointment Booking System – Bookly
Affected Version
<= 27.7
CVSS
7.2High
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-13424
View all Online Scheduling and Appointment Booking System – Bookly vulnerabilities

At a glance

CVE-2026-13424 is a high-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Online Scheduling and Appointment Booking System WordPress plugin, affecting versions <= 27.7. It carries a CVSS score of 7.2 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 28.0; sites on affected versions should update now. Disclosed August 2026, reported by Dmitrii Ignatyev.

Vulnerability Overview

The Online Scheduling and Appointment Booking System – Bookly plugin for WordPress is vulnerable to Stored Cross-Site Scripting via bookly_speed_up_update_addons AJAX action in all versions up to, and including, 27.7 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The injection point is the bookly_speed_up_update_addons AJAX action, which is registered as wp_ajax_nopriv_* and therefore reachable without authentication; the payload is stored verbatim in the bookly_log.details column when a request is submitted without a valid signature, and executes when an administrator later views the Diagnostics → Logs page.

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.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in Online Scheduling and Appointment Booking System <= 27.7 takes no account at all. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Online Scheduling and Appointment Booking System the fix is 28.0: builds <= 27.7 are affected, anything from 28.0 onward is not.

Remediation

Update to version 28.0, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Online Scheduling and Appointment Booking System 28.0 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-13424https://www.wordfence.com/threat-intel/vulnerabilities/id/cfb53e44-7f9d-490f-b938-f428c20219d7https://nvd.nist.gov/vuln/detail/CVE-2026-13424

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C