High
CVSS 8.6 Webhook Forgery Responsible Disclosure
Disclosure
Unauthenticated Payment Event Injection via Partner Callback
Partner callback endpoint has no signature check so attackers can inject arbitrary payment events for any merchant.
- Target
- European Payment Gateway
- Category
- Webhook Forgery
- Channel
- Responsible Disclosure
- 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 Responsible Disclosure 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.