CVE-2026-13400

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

Score 6.1 from GitHub Security Advisory published 2026-07-27. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 6.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 3 sources updated this weekElevated
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.1
EG Score
6.1(medium)
EG Risk
43(Track)
EG Risk 43/100SSVC: 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 computed
Severity61% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
4%
KEV
Not listed

Published

July 27, 2026

Last Modified

July 27, 2026

Advisory Details (1)

Auto-updated Jul 27, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic🟡 PoC Available

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

https://wpscan.com/vulnerability/501b2929-3216-4587-8124-088fd51becf1/

Vendor Advisories for CVE-2026-13400(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 17× in last 7d / 65× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 128 total refreshes for this CVE.

  1. 2026-09-15 09:16 UTCEG score recompute
  2. 2026-09-15 09:16 UTCGHSA enrichment
  3. 2026-09-13 18:26 UTCEG score recompute
  4. 2026-09-13 18:26 UTCGHSA enrichment
  5. 2026-09-13 16:46 UTCEPSS rescore
  6. 2026-09-12 17:10 UTCEG score recompute
  7. 2026-09-12 17:10 UTCGHSA enrichment
  8. 2026-09-12 15:00 UTCEPSS rescore
  9. 2026-09-11 15:54 UTCEG score recompute
  10. 2026-09-11 15:54 UTCGHSA enrichment
  11. 2026-09-11 14:52 UTCEPSS rescore
  12. 2026-09-11 09:36 UTCEPSS rescore
  13. 2026-09-10 10:21 UTCEG score recompute
  14. 2026-09-10 10:21 UTCGHSA enrichment
  15. 2026-09-10 09:34 UTCEPSS rescore
  16. 2026-09-09 08:26 UTCEG score recompute
  17. 2026-09-09 08:26 UTCGHSA enrichment
  18. 2026-09-08 22:00 UTCEPSS rescore
  19. 2026-09-08 01:04 UTCEG score recompute
  20. 2026-09-08 01:04 UTCGHSA enrichment
  21. 2026-09-07 16:01 UTCEPSS rescore
  22. 2026-09-06 23:48 UTCEG score recompute
  23. 2026-09-06 23:47 UTCGHSA enrichment
  24. 2026-09-06 13:47 UTCEPSS rescore
  25. 2026-09-05 19:17 UTCEG score recompute
Show 75 more
  1. 2026-09-05 19:17 UTCGHSA enrichment
  2. 2026-09-04 12:36 UTCEG score recompute
  3. 2026-09-04 12:36 UTCGHSA enrichment
  4. 2026-09-04 05:06 UTCEPSS rescore
  5. 2026-09-02 14:11 UTCEPSS rescore
  6. 2026-09-01 23:04 UTCEG score recompute
  7. 2026-09-01 23:04 UTCGHSA enrichment
  8. 2026-09-01 13:53 UTCEPSS rescore
  9. 2026-09-01 04:39 UTCEPSS rescore
  10. 2026-08-31 01:13 UTCEG score recompute
  11. 2026-08-31 01:13 UTCGHSA enrichment
  12. 2026-08-30 19:17 UTCEPSS rescore
  13. 2026-08-30 01:21 UTCEPSS rescore
  14. 2026-08-29 23:58 UTCEG score recompute
  15. 2026-08-29 23:58 UTCGHSA enrichment
  16. 2026-08-28 21:40 UTCEPSS rescore
  17. 2026-08-27 14:24 UTCEPSS rescore
  18. 2026-08-27 10:10 UTCEG score recompute
  19. 2026-08-27 10:10 UTCGHSA enrichment
  20. 2026-08-26 08:54 UTCEG score recompute
  21. 2026-08-26 08:54 UTCGHSA enrichment
  22. 2026-08-25 13:48 UTCEPSS rescore
  23. 2026-08-25 07:31 UTCEG score recompute
  24. 2026-08-25 07:31 UTCGHSA enrichment
  25. 2026-08-24 06:14 UTCGHSA enrichment
  26. 2026-08-23 04:44 UTCEG score recompute
  27. 2026-08-23 04:44 UTCGHSA enrichment
  28. 2026-08-23 00:19 UTCEPSS rescore
  29. 2026-08-22 03:28 UTCEG score recompute
  30. 2026-08-22 03:28 UTCGHSA enrichment
  31. 2026-08-21 23:48 UTCEPSS rescore
  32. 2026-08-21 02:12 UTCEG score recompute
  33. 2026-08-21 02:12 UTCGHSA enrichment
  34. 2026-08-20 22:55 UTCEPSS rescore
  35. 2026-08-20 00:56 UTCGHSA enrichment
  36. 2026-08-18 23:29 UTCEG score recompute
  37. 2026-08-18 23:29 UTCGHSA enrichment
  38. 2026-08-18 13:48 UTCEPSS rescore
  39. 2026-08-17 22:13 UTCEG score recompute
  40. 2026-08-17 22:13 UTCGHSA enrichment
  41. 2026-08-16 20:57 UTCEG score recompute
  42. 2026-08-16 20:57 UTCGHSA enrichment
  43. 2026-08-16 14:56 UTCEPSS rescore
  44. 2026-08-16 02:14 UTCEPSS rescore
  45. 2026-08-15 19:41 UTCEG score recompute
  46. 2026-08-15 19:41 UTCGHSA enrichment
  47. 2026-08-15 01:30 UTCEPSS rescore
  48. 2026-08-14 18:25 UTCEG score recompute
  49. 2026-08-14 18:25 UTCGHSA enrichment
  50. 2026-08-13 22:00 UTCEPSS rescore
  51. 2026-08-13 17:09 UTCGHSA enrichment
  52. 2026-08-12 15:54 UTCEG score recompute
  53. 2026-08-12 15:54 UTCGHSA enrichment
  54. 2026-08-12 13:50 UTCEPSS rescore
  55. 2026-08-11 14:38 UTCEG score recompute
  56. 2026-08-11 14:38 UTCGHSA enrichment
  57. 2026-08-11 13:42 UTCEPSS rescore
  58. 2026-08-10 23:59 UTCEPSS rescore
  59. 2026-08-10 13:23 UTCEG score recompute
  60. 2026-08-10 13:23 UTCGHSA enrichment
  61. 2026-08-09 13:46 UTCEPSS rescore
  62. 2026-08-09 12:06 UTCEG score recompute
  63. 2026-08-09 12:06 UTCGHSA enrichment
  64. 2026-08-08 16:37 UTCEPSS rescore
  65. 2026-08-08 10:50 UTCEG score recompute
  66. 2026-08-08 10:50 UTCGHSA enrichment
  67. 2026-08-07 09:34 UTCEG score recompute
  68. 2026-08-07 09:34 UTCGHSA enrichment
  69. 2026-08-06 13:46 UTCEPSS rescore
  70. 2026-08-06 08:18 UTCEG score recompute
  71. 2026-08-06 08:18 UTCGHSA enrichment
  72. 2026-08-05 19:17 UTCEPSS rescore
  73. 2026-08-05 07:02 UTCEG score recompute
  74. 2026-08-05 07:02 UTCGHSA enrichment
  75. 2026-08-04 15:09 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-13400?
CVE-2026-13400 is a medium vulnerability published on July 27, 2026. 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…
When was CVE-2026-13400 disclosed?
CVE-2026-13400 was first published in the National Vulnerability Database on July 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-13400 actively exploited?
CVE-2026-13400 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 95.9% of all scored CVEs.
What is the CVSS score of CVE-2026-13400?
CVE-2026-13400 has a CVSS v3.1 base score of 6.1 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-13400?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-13400, 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.

Dependency Blast Radius

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