XSS in Simply Schedule Appointments
CVE-2026-13400
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.
Vulnerability class: XSS (Cross-Site Scripting)
EPSS: 0.001 (4.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Unknown Simply Schedule Appointments — versions 0
Weakness classification (CWE)
References
- contact@wpscan.com (technical-description, exploit, vdb-entry)
Frequently asked questions
- What is CVE-2026-13400?
- CVE-2026-13400 is a medium-severity vulnerability in Simply Schedule Appointments, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-07-27.
- How severe is CVE-2026-13400?
- Medium severity. CVSS v3 base score is 6.1 out of 10.