Unauthenticated stored XSS via decoded booking data
Published Jul 27, 2026 · Updated Jul 27, 2026
Stored XSS in Simply Schedule Appointments before 1.6.12.4 allows remote attackers to inject script through booking customer information. The notification path sanitizes nested customer_information before decoding it, so double-encoded markup is restored as executable HTML at render time. No WordPress account is required, but execution requires a user to render notification content containing attacker-supplied booking data.
Summary
What happened
Stored XSS in Simply Schedule Appointments before 1.6.12.4 allows remote attackers to inject script through booking customer information. The notification path sanitizes nested customer_information before decoding it, so double-encoded markup is restored as executable HTML at render time. No WordPress account is required, but execution requires a user to render notification content containing attacker-supplied booking data.
The record
- CVE
- CVE-2026-13400
- Published
- Jul 27, 2026
- Updated
- Jul 27, 2026
- Vendor
- N Squared Digital, LLC
- Product
- Simply Schedule Appointments
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 27, 2026CVE publishedPublication date reported by the CVE source.
- Jul 27, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <1.6.12.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- WPScan decode-after-sanitization stored XSS proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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