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CVE-2026-63428

MEDIUM Exploitation: PoC
5.8
CVSS 3.1
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.

Metadata

CVE ID
CVE-2026-63428
State
PUBLISHED
Assigner
GitHub_M
Reserved
2026-07-16 19:35 UTC
Published
2026-07-20 15:50 UTC
Last updated
2026-07-20 16:13 UTC
Primary CWE
CWE-20
CWE-20: Improper Input Validation
Vendor / Product
heyform / heyform
Sources
cve.org  ·  NVD

Severity & Metrics

5.8 MEDIUM CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
SSVC — CISA Coordinator
Exploitation
PoC
Automatable
yes
Tech. Impact
partial
Affected products (1)
VendorProductPlatformVersions
heyform heyform — < 3.0.0-rc.9
Weakness (CWE)
CWESourceDescription
CWE-20 cna CWE-20: Improper Input Validation
CWE-915 cna CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes
CVSS scores (1)
ScoreSeverityVersionSourceVector
5.8 MEDIUM 3.1 cna CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
References (2)
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