# CVE-2026-63428

## Summary

- **CVE ID:** CVE-2026-63428
- **Severity:** MEDIUM
- **CVSS Score:** 5.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N)
- **CWE:** CWE-20, CWE-915
- **Published:** Jul 20, 2026
- **Last Modified:** Jul 20, 2026

## Description

HeyForm is an open-source form builder. Prior to version 3.0.0-rc.9, `completeSubmission` accepts a `hiddenFields: [{id, name, value}]` array from the submitter and stores it verbatim in `submission.hiddenFields`, without validating the supplied `id`/`name` against the form's declared `form.hiddenFields` schema. An anonymous form submitter can therefore inject arbitrary key/value pairs (including XSS payloads, fake authorization metadata, integration-relevant values) into the stored submission. These fields are subsequently forwarded as-is to every webhook integration registered on the form. Version 3.0.0-rc.9 contains a patch for the issue.

## Affected Products

- heyform — heyform (< 3.0.0-rc.9)

## References

- [CNA](https://github.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3)
- [CNA](https://github.com/heyform/heyform/commit/092e255e9e02565de1b3c057f3dad849160952d2)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.34%
- **EPSS Percentile:** 27.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._