# CVE-2026-19857: Formidable Forms < 6.35 - Unauthenticated Arbitrary Shortcode Execution via [entry_key] Custom HTML Token

> Unauthenticated attackers can execute arbitrary shortcodes via custom HTML tokens in Formidable Forms, potentially leading to server-side code execution.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-hgfq-v6h8-89x5

## What is CVE-2026-19857?

CVE-2026-19857 is a medium-severity code injection vulnerability in Unknown Formidable Forms, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Formidable Forms WordPress plugin before 6.35 does not prevent a request-derived value from reaching the WordPress shortcode parser when it substitutes a supported token into a form's custom HTML, allowing unauthenticated visitors to have arbitrary shortcodes, with attacker-chosen attributes, executed server-side on any page displaying an affected form.

Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component)

## Which versions are affected by CVE-2026-19857?


## How do I fix CVE-2026-19857?

No fix has been published for CVE-2026-19857 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-19857 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19857 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19857 and fix it if it is affected.

What it is: CVE-2026-19857 is a medium-severity code injection vulnerability in Unknown Formidable Forms, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19857 exists.

Affected product: Unknown Formidable Forms. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19857/ (Markdown: https://insights.sbomify.com/CVE-2026-19857/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19857
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19857
- OSV: https://osv.dev/vulnerability/CVE-2026-19857

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19857/
Summaries are generated and may contain mistakes; the official description above is the record.