# CVE-2026-100155: Ninja Forms <= 3.15.5 - Unauthenticated Arbitrary Shortcode Execution via 'formData' Field Value via Success Message Merge Tag

Status: published. Published: 2026-10-31. Updated: 2026-11-02.

The The Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder plugin for WordPress is vulnerable to arbitrary shortcode execution in all versions up to, and including, 3.15.5 This is due to the software allowing users to execute an action that does not properly validate a value before running do_shortcode. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- kstover / Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder: ≥ 0; ≤ 3.15.5 (affected, semver). Source: CNA: Wordfence

## Severity and prioritization

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N; source: CNA: Wordfence

- CISA KEV: No listing in collected sources

- EPSS: 0.51% as of 2026-11-02; percentile 43.81%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-94

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/a1cf42f7-77c6-4594-a6a4-cebf5c3558d7?source=cve (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/Actions/SuccessMessage.php#L63 (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/Actions/SuccessMessage.php#L70 (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/AJAX/Controllers/Submission.php#L52 (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/Abstracts/MergeTags.php#L64 (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/MergeTags/Fields.php#L268 (CNA: Wordfence)

- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/AJAX/Controllers/Submission.php#L60 (CNA: Wordfence)

- https://wordpress.org/plugins/ninja-forms/ (CNA: Wordfence)

- https://plugins.trac.wordpress.org/changeset?reponame=&new=3749135%40ninja-forms%2Ftags%2F3.15.6&old=3717122%40ninja-forms%2Ftags%2F3.15.5 (CNA: Wordfence)

## Provenance

- CNA: Wordfence: https://www.cve.org/CVERecord?id=CVE-2026-100155; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-100155; retrieved 2026-11-02; source updated Not reported

Revision: 9d2332541f2f262027af13192481ecb807b46d376cc6b6d25f99646ec4c715d3

Canonical: https://y2.dev/cve/CVE-2026-100155

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.