What’s Vulnerable › Vulnerabilities

CVE-2026-63428: HeyForm: completeSubmission persists submitter-supplied hidden fields verbatim without validating against the form's declared hidden-field set

• Severity: medium (CVSS 5.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-20 · updated 2026-07-22
• Weakness: CWE-20

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: before 3.0.0-rc.9

References

• https://github.com/heyform/heyform/commit/092e255e9e02565de1b3c057f3dad849160952d2
• https://github.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3
• https://github.com/heyform/heyform/security/advisories/GHSA-r7vg-xh87-v4w3

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