High
CVSS 8.6 KYC Bypass HackerOne
Disclosure
SumSub Webhook Without Signature Verification
Vulnerable Endpoint: https://test.[vendor]/kyc/sumsub_webhook/
- Target
- EU Crypto Exchange
- Category
- KYC Bypass
- Channel
- HackerOne
- Disclosed
- 2026-04
Redaction note
Vendor identity withheld.
This finding is documented here as part of MemCyber’s public disclosure record. The vendor has been anonymized to a sector and region descriptor. Full technical detail — including root cause, reproducible proof-of-concept, remediation guidance, and vendor attribution where granted — is available to qualified prospects under NDA.
Coordinated disclosure
How we handled it.
- Reported to the vendor via HackerOne with a reproducible proof-of-concept.
- Triage + remediation window coordinated with the vendor security team.
- Fix verified before any public reference.
- This record published only after the embargo period closed.