CVE-2026-63428 Business logic in heyform
Attackers can inject arbitrary hidden fields into form submissions, bypassing validation and potentially triggering XSS or unauthorized actions in downstream integrations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-63428?
CVE-2026-63428 is a medium-severity vulnerability in heyform, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-63428?
How do I fix CVE-2026-63428?
No fix has been published for CVE-2026-63428 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-63428 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-63428 exists.
Sources
Also known as GHSA-r7vg-xh87-v4w3.