CVE-2026-13400: Simply Schedule Appointments (WordPress plugin) · Cross-Site Scripting (XSS)
Affects Simply Schedule Appointments (WordPress plugin)Source CVE Database V5
Not known to be exploited · CVSS 6.1 Medium : upgrade to 1.6.12.4 when convenient.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 16% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.6.12.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 27 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade Simply Schedule Appointments (WordPress plugin) to 1.6.12.4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Simply Schedule Appointments | Affected
| Fixed in
|
AI-suggested
The vulnerability is fixed starting from version 1.6.12.4 by correcting the sanitization order with the wp_kses_post() filter. Until patching, avoid exposing notification content to untrusted users or disable the affected plugin if possible.
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.