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CVE-2026-63428

MediumCVSS 5.8 / 10
Published Jul 20, 2026·Last modified Jul 21, 2026
Affected Components(0)

No affected components available

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.

Risk Scores
Base Score
5.8

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the integrity of the data.

Threat Intelligence
5.3

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.25%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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