Open Banking API Security: Risks & Best Practices

Open banking API security protects the financial data that moves between banks and the third parties customers authorize. It covers encryption, authentication, consent and monitoring, working together as layers. Without it, every new connection becomes a new way in for attackers.

Open banking APIs unlock real value. Customers can pay straight from their bank account, share their data with budgeting apps and get faster credit decisions. We use them every day at ConnectPay, for example when merchants accept bank payments instead of cards. But each API also expands the attack surface for some of the most sensitive data a person has.

This guide covers the main risks, the security practices that address them, and how regulation differs across the EU, Australia and the US. We also explain what to look for when you choose an open banking platform, so you can judge api security on evidence rather than marketing claims.

Why Open Banking API Security Matters

Open banking moves financial data out of a single bank and into a network of apps, processors and data platforms. That’s the point of it. It’s also the risk.

Every API connection gives attackers another place to try. They can target data in transit, as it moves between a bank and a third party. They can also target data at rest, stored in the third party’s systems. A weak link anywhere in the chain exposes the whole flow.

A common mistake we see is treating OAuth as the whole answer. OAuth handles authorization: it lets a customer grant an app access without sharing their banking password. That’s essential. But OAuth doesn’t stop injection attacks, broken access controls or leaked tokens. API security in open banking has to be designed into every layer, from the network to the application code to the logs.

Regulation adds another layer of complexity. The EU and Australia have settled, enforced frameworks. The US does not, and its rules remain in flux. We cover that in detail below, because your compliance obligations depend heavily on where you operate. For now, the key point is simple: open banking api security is your responsibility, whatever your regulator requires.

Common Open Banking API Security Risks

Building secure open banking APIs starts with knowing what you’re defending against. These are the risks we see most often:

• Shadow APIs. Teams under deadline pressure ship test endpoints or old versions that nobody tracks. These APIs bypass security controls, and attackers find them.
• Injection attacks. When an API doesn’t sanitize inputs properly, attackers can slip malicious commands into a request and reach the database behind it.
• Denial-of-service attacks. Automated requests flood an API until it slows down or stops, blocking real customers from paying or logging in.
• Credential stuffing. Attackers take usernames and passwords leaked from other sites and try them in bulk against your login API.
• Weak identity claims. If the API trusts identity claims without verifying them properly, an attacker can access accounts that aren’t theirs.
• Phishing and social engineering. Fraudsters trick customers into approving access for a fake app, or trick staff into granting permissions.
• Unauthorized third-party access. A third party gets more access to bank accounts than the customer agreed to, or keeps access after consent ends.

Poor logging makes all of these worse. If you don’t record who called which API and what data left, you can’t spot data exfiltration, and you can’t trace it after the fact. For a wider view of how providers handle these issues, see our overview of open banking solutions.

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Open Banking API Security Best Practices

Strong banking api security comes from layers, not a single control. These open banking api security best practices cover the main ones.

• Encrypt everything in transit and at rest. Use TLS 1.3 for data in transit. Use AES encryption, typically AES-256, for stored data.
• Use OAuth with FAPI 2.0. The OpenID Foundation’s Financial-grade API (FAPI) 2.0 profiles harden OAuth for high-security financial use. They close gaps that basic OAuth setups leave open.
• Sender-constrain your access tokens. A standard token works for anyone who holds it. A sender-constrained token, bound through mTLS or DPoP, only works for the client it was issued to. Stolen tokens become useless, and replay attacks fail.
• Apply rate limiting. Cap how many requests each client and IP address can make. This blocks credential stuffing and limits DoS damage.
• Manage consent and scope granularly. A budgeting app that needs 90 days of transactions shouldn’t get payment rights. Grant only the data and actions the customer approved.
• Route traffic through an API gateway. Gateways enforce authentication, rate limits and policies in one place, so no endpoint slips through.
• Monitor behavior continuously. Correlate API activity with fraud signals. A third party that suddenly pulls data on thousands of accounts at night needs attention. Our own fraud prevention works on the same principle.
• Assess third parties before granting access. Check their security posture, certifications and history before they connect.
• Audit regularly. Run penetration tests and security reviews on a fixed schedule.

Finally, build ways to revoke access and respond to incidents. These aren’t optional extras. When a token leaks or a partner gets breached, you need to cut access in minutes, not days.

Open Banking Regulations and Standards

Open banking regulations differ sharply by region.

EU: PSD2

The Payment Services Directive (PSD2) requires Strong Customer Authentication (SCA) for open banking APIs. Customers must confirm payments and access with multi-factor authentication. The framework is settled and enforced.

EU: GDPR

GDPR isn’t an open banking regulation. It works alongside PSD2 as a general data protection layer. It gives consumers control over their personal financial data, including how long a provider keeps it and who sees it.

Australia: Consumer Data Right

Australia’s Consumer Data Right (CDR) governs open banking data sharing there. Like PSD2, it’s settled and enforced.

US: Section 1033

The US picture is far less clear. The CFPB finalized its Section 1033 “open banking” rule in October 2024. A federal court has since enjoined the CFPB from enforcing it while the Bureau reconsiders the rule. The first compliance date of April 1, 2026 passed without effect. In August 2026, the CFPB sent a revised proposal for federal review. In short, the rule exists on paper but isn’t currently enforceable, unlike the EU and Australian frameworks.

FAPI

Across all regions, FAPI is emerging as the shared technical standard for high-security financial APIs. Australia’s CDR already builds on it, and many EU and UK providers use it too.

Benefits of Secure Open Banking APIs

Security matters because the upside is real. When open banking APIs are secure, businesses and customers both gain.

• One view of your money. Customers can see accounts from several banks in one dashboard. That makes budgeting and planning much easier.
• More competition. New providers can build products on top of bank data, from instant payments to direct debit alternatives. Customers get more choice.
• Financial inclusion. People with thin credit files can share real transaction history instead. A lender can see steady rent payments and approve a loan that a credit score alone would reject.
• Real-time risk assessment. Lenders and platforms can assess risk using live financial data, not month-old statements.

For merchants, the gains show up at checkout too. Bank payments can mean high conversion at low cost.

The market reflects this. Industry estimates put the global open banking market somewhere in the $30–45 billion range as of 2025–2026, with strong growth projected over the next decade. Analyst figures vary, but they all point in the same direction.

Platforms Known for Strong Open Banking API Security

This isn’t a ranking, but a few names come up often when teams look for the best open banking api platforms for security.

• Plaid connects apps to bank accounts at scale, mainly in the US, and has invested heavily in API-based bank connections.
• TrueLayer runs open banking payments and data across the UK and Europe.
• Tink, owned by Visa, provides account data and payments across many European markets.
• Token.io focuses on account-to-account payment infrastructure for banks and payment providers.

Don’t take any provider’s security claims at face value, including these. Look for concrete signals. FAPI 2.0 adoption and granular consent management say more about security maturity than any marketing page. For a wider list of API providers, see our guide to the best fintech API companies.

How to Choose a Secure Open Banking API Platform

When you compare platforms, test them against open banking api security standards, not their sales decks. Ask these five questions.

1. Has the platform adopted FAPI profiles? Ask which version and for which flows. FAPI 2.0 is the current benchmark.
2. How granular is consent and scope management? Can customers grant read-only access? Can they limit it to specific accounts or a time period?
3. What happens during an incident? Ask how fast the platform can revoke access, who it notifies and how it reports breaches.
4. Does it comply in your regions? Check its compliance posture for each market you serve. Strong UK coverage doesn’t guarantee strong EU coverage.
5. What does it log and monitor? You need detailed API logs and alerts for unusual activity, plus access to them when you investigate.

Remember that compliance is a floor, not a ceiling. A platform can pass PCI DSS and still have weak API design. Real security maturity goes beyond checkbox compliance. That’s how we approach embedded compliance for our clients: the rules set the minimum, and good practice goes further.

Make Open Banking Security a Foundation, Not an Afterthought

Open banking API security doesn’t come from one control. It comes from layered defenses working together: encryption, strong authentication, granular consent and continuous monitoring. Remove any one layer, and the others carry more weight than they should.

Treat regulation as your starting point, not your full strategy. PSD2 and the CDR set clear minimums. In the US, the Section 1033 rule remains stalled, so businesses there can’t rely on regulation to define good practice. The teams that do best build to strong standards like FAPI now, whatever their regulator requires.

Our advice is practical. Design security in from the first API call. Test your partners before you connect them. And plan how you’ll cut off access before you ever need to.

To see how we handle payments, accounts and compliance together, visit ConnectPay.