High severity · published Oct 16, 2026
CVE-2026-104000
Simply Schedule Appointments <= 1.6.12.35 - Unauthenticated Stored Cross-Site Scripting via 'status' Parameter via /wp-json/ssa/v1/appointments/{id}
7.2
CVSS
0.2%
EPSS
No
On KEV
Description
The Simply Schedule Appointments plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'status' parameter in all versions up to, and including, 1.6.12.35 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 malicious payload is stored unconditionally because debug logging is enabled by default, and the debug-log viewer is accessible to anyone holding the site-wide Support PIN (an HMAC-MD5 of AUTH_SALT displayed in wp-admin), meaning the injected script will execute against the administrator's session during ordinary support or troubleshooting workflows.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 15% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SS
Simply Schedule Appointments · croixhaug
through 1.6.12.35 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-104000
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-104000
plugins.trac.wordpress.org
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.33/includes/class-appointment-model.php#L1490
plugins.trac.wordpress.org
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.33/includes/class-debug.php#L92
plugins.trac.wordpress.org
https://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.33/includes/class-utils.php#L716
plugins.trac.wordpress.org
https://plugins.trac.wordpress.org/changeset/3746344/simply-schedule-appointments/trunk/includes/class-appointment-model.php
www.wordfence.com
https://www.wordfence.com/threat-intel/vulnerabilities/id/3a8bd422-112c-43bc-a041-3c6eea27b790?source=cve
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