The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.6.12.10 via the ssa_past_appointments due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with contributor-level access and above, to access appointment records belonging to arbitrary users and harvest the per-appointment ownership tokens (32-character hashes) embedded in the rendered HTML, which can then be used without any authentication to read or modify those appointments including full customer PII such as name, email, phone number, and private notes. The /wp-json/ssa/v1/render-shortcode REST endpoint is registered unconditionally on rest_api_init regardless of whether the Divi theme is installed, and its permission callback only requires current_user_can('edit_posts'), meaning any Contributor-level account is sufficient to trigger this entire exploit chain.
CVE-2026-13358
MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence
Score 6.5 from GitHub Security Advisory published 2026-08-16. a secondary CVSS source baseline 6.5; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
- Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 6.5
- EG Score
- 6.5(medium)
- EG Risk
- 29(Track)EG Risk 29/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity65% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 41%
- KEV
- Not listed
Published
August 16, 2026
Last Modified
August 20, 2026
References (12)
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-appointment-model.php#L1936
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-db-model.php#L325
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-divi.php#L237
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-divi.php#L254
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.11.0/includes/class-shortcodes.php#L781
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.4/includes/class-appointment-model.php#L1936
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.4/includes/class-db-model.php#L325
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.4/includes/class-divi.php#L237
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.4/includes/class-divi.php#L254
- security@wordfencehttps://plugins.trac.wordpress.org/browser/simply-schedule-appointments/tags/1.6.12.4/includes/class-shortcodes.php#L781
- security@wordfencehttps://plugins.trac.wordpress.org/changeset?reponame=&old=3617759%40simply-schedule-appointments&new=3617759%40simply-schedule-appointments
- security@wordfencehttps://www.wordfence.com/threat-intel/vulnerabilities/id/5dbe5094-d255-46b1-9e8e-9c48cd74e8a2?source=cve
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Frequently asked(5)
What is CVE-2026-13358?
CVE-2026-13358 is a medium vulnerability published on August 16, 2026. The Appointment Booking Calendar — Simply Schedule Appointments Booking Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.6.12.10 via the ssapastappointments due to missing validation on a user controlled key. This makes it…
When was CVE-2026-13358 disclosed?
CVE-2026-13358 was first published in the National Vulnerability Database on August 16, 2026, with the most recent update on August 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-13358 actively exploited?
CVE-2026-13358 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 59.3% of all scored CVEs.
What is the CVSS score of CVE-2026-13358?
CVE-2026-13358 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-13358?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-13358, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
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