Vulnerability · Published Jul 27, 2026 · Assigned by WPScan

CVE-2026-13400Simply Schedule Appointments < 1.6.12.4 - Unauthenticated Stored XSS via Booking Customer Information

Medium 6.1

In plain English

A medium-severity cross-site scripting in Simply Schedule Appointments from Unknown. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 17% of all known vulnerabilities).

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.3%top 83.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
Unknown	Simply Schedule Appointments	0 – before 1.6.12.4

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

https://wpscan.com/vulnerability/501b2929-3216-4587-8124-088fd51becf1/ exploit, vdb-entry, technical-description