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PatchSiren cyber security CVE debrief

CVE-2026-35198 heyform CVE debrief

A stored cross-site scripting (XSS) vulnerability in HeyForm's form builder allows low-privileged team members to inject malicious JavaScript that executes when a team owner views the form, leading to complete account takeover through privilege escalation. The issue was patched in version 3.0.0-rc.7. This vulnerability affects users of HeyForm, especially those with low-privileged team members, and could lead to account takeovers if not addressed. The vulnerability exists due to insufficient input validation and sanitization in the form builder feature.

Vendor
heyform
Product
Unknown
CVSS
CRITICAL 9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-20
Original CVE updated
2026-08-21
Advisory published
2026-07-20
Advisory updated
2026-08-21

Who should care

Users of HeyForm, especially those with low-privileged team members, should be aware of this vulnerability and ensure they are using version 3.0.0-rc.7 or later to prevent potential account takeovers. Affected operator, platform, vulnerability-management, and security-team impact should be reviewed.

Technical summary

The vulnerability exists in the form builder of HeyForm, allowing low-privileged team members to inject malicious JavaScript. This JavaScript executes when a team owner views the form, potentially leading to complete account takeover. The vulnerability was patched in version 3.0.0-rc.7. Affected product deployments should be verified, and compensating controls should be reviewed while remediation is scheduled and verified.

Defensive priority

High

Recommended defensive actions

  • Update HeyForm to version 3.0.0-rc.7 or later
  • Restrict form building privileges to trusted team members
  • Monitor form usage and team member activity
  • Implement additional security measures to prevent account takeover
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-20T16:16:58.440Z and last modified on 2026-07-20T19:17:21.537Z. The NVD entry is currently being reviewed. A stored cross-site scripting (XSS) vulnerability in HeyForm's form builder allows low-privileged team members to inject malicious JavaScript that executes when a team owner views the form, leading to complete account takeover through privilege escalation. The issue was patched in version 3.0.0-rc.7. Evidence limits suggest that affected deployments and configurations should be verified with the vendor and through internal reviews.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-35198 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-35198

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-35198 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-35198

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.