CVE-2026-63428
Severity CVSS v4.0:
Pending analysis
Type:
CWE-20
Input Validation
Publication date:
20/07/2026
Last modified:
20/07/2026
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.
Impact
Base Score 3.x
5.80
Severity 3.x
MEDIUM