Open banking integrations move real account data and payment rails through third-party connections, which makes API security a regulatory requirement, not just an engineering preference. This checklist covers what a fintech, lender, or payments platform should have in place before connecting to or exposing open banking APIs — whether you're building on India's Account Aggregator framework, UK/EU open banking standards, or a bilateral bank API partnership.

Who this is for

Engineering leads, CTOs, and compliance officers at fintechs, lenders, and payment platforms planning or reviewing an open banking API integration.

Authentication and transport security

  • [ ] TLS 1.3 enforced on every API endpoint, with weaker TLS versions explicitly disabled at the gateway.
  • [ ] Mutual TLS (mTLS) in place for server-to-server authentication with third-party providers (TPPs) — client certificates verified, not just presented.
  • [ ] OAuth 2.0 / OpenID Connect implemented for delegated authorization, with Pushed Authorization Requests (PAR) and PKCE enabled for all clients.
  • [ ] Sender-constrained access tokens (via mTLS or DPoP) to prevent token replay if a token is intercepted.
  • [ ] FAPI (Financial-grade API) security profile evaluated for adoption — increasingly a baseline expectation even outside jurisdictions that mandate it.
  • [ ] A dedicated consent API supporting the full lifecycle: grant, update, revoke, and audit — not a one-time checkbox buried in onboarding.
  • [ ] Every data access scoped and time-limited to what the customer actually consented to, with automatic expiration.
  • [ ] Consent revocation triggers an immediate, verifiable halt to data access — test this, don't assume it.
  • [ ] If operating under India's Account Aggregator framework: confirm your architecture never stores or reuses data beyond the consented purpose, and that consent artefacts specify purpose, recipients, and expiration explicitly.
  • [ ] Row-level security and attribute-based access control (ABAC) tied to specific consent scopes, not broad account-level permissions.

Third-party and vendor risk

  • [ ] A formal TPP (third-party provider) due diligence and risk assessment process before granting API access — not just a signed agreement.
  • [ ] API gateway enforcing rate limits, payload schema validation, and anomaly detection on every connected TPP.
  • [ ] Contractual and technical controls for what happens if a connected TPP is breached — do you have a kill switch for their access?

Monitoring and incident response

  • [ ] Centralized, actively monitored logging across all API traffic — not logs that only get reviewed after an incident.
  • [ ] Anomaly detection tuned for excessive or unusual data request patterns, not just failed-login thresholds.
  • [ ] An incident response plan written specifically for an API breach scenario, tested at least annually.
  • [ ] Regular independent penetration testing focused on API endpoints, not just the web application layer.

Input validation and data protection

  • [ ] Strict input validation and schema enforcement at the API gateway for every payload, inbound and outbound.
  • [ ] AES-256 encryption for sensitive data at rest; tokenization for sensitive fields wherever full values aren't operationally necessary.
  • [ ] Injection-attack protections tested as part of every release, not just at initial launch.

Red flags to watch for

  • [ ] A TPP integration proposal with no documented consent-revocation flow.
  • [ ] Any API partner unwilling to support mTLS or provide verifiable certificate chains.
  • [ ] Logging that isn't centralized — scattered logs are functionally unmonitored logs.
  • [ ] A pen test scope that excludes the API layer because "the web app was already tested."

How to use this

Run this against any open banking integration before it goes live, and again annually for existing connections — TPP risk and regulatory expectations both shift faster than most integration reviews get scheduled. The consent and third-party risk sections are the two most commonly skipped in practice; don't let engineering timelines compress those.