CVE-2026-13400

Simply Schedule Appointments < 1.6.12.4 - Unauthenticated Stored XSS via Booking Customer Information

Published Jul 27, 2026 CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed
Description
Simply Schedule Appointments is vulnerable to unauthenticated Stored Cross-Site Scripting in all versions up to and including 1.6.12.2. The root cause is a sanitization-ordering defect: the rendered notification content is decoded back into live HTML after it has already passed through the Simply Schedule Appointments WordPress plugin before 1.6.12.4's wp_kses_post() filter, so a double-encoded payload survives intake and is reintroduced as an executable element at render time.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Nsquared
Nsquared simply Schedule Appointments
Wordpress
Wordpress wordpress
Vendors & Products Nsquared
Nsquared simply Schedule Appointments
Wordpress
Wordpress wordpress
Type Values Removed Values Added
Weaknesses CWE-79
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Simply Schedule Appointments is vulnerable to unauthenticated Stored Cross-Site Scripting in all versions up to and including 1.6.12.2. The root cause is a sanitization-ordering defect: the rendered notification content is decoded back into live HTML after it has already passed through the Simply Schedule Appointments WordPress plugin before 1.6.12.4's wp_kses_post() filter, so a double-encoded payload survives intake and is reintroduced as an executable element at render time.
Title Simply Schedule Appointments < 1.6.12.4 - Unauthenticated Stored XSS via Booking Customer Information
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
WPScan
Published
Updated
Jul 27, 2026, 1:53 PM
Reserved
Jun 26, 2026, 8:35 AM
Status
Deferred
Published
Jul 27, 2026, 7:16 AM
Modified
Jul 27, 2026, 8:33 PM