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.
{
"cna_assigner": "GitHub_M",
"cwe_ids": [
"CWE-20",
"CWE-915"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63428.json"
}{
"extracted_events": [
{
"range": [
{
"introduced": "0"
},
{
"fixed": "3.0.0-rc.9"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
{
"fixed": "092e255e9e02565de1b3c057f3dad849160952d2"
}
],
"source": "REFERENCES_COMMIT"
}
]
}