Is Open Banking safe? How does banking API security work? If Open Banking and security are on your list of worries right now, let us help. Below, we’ll unpack all you need to know about Open Banking security, from top threats and vulnerabilities to the three pillars of a bulletproof Open Banking security strategy.
Read on to put all your banking security system worries to bed.
What is Open Banking used for?
Let’s get the basics out of the way first. Open Banking is used to open up customers’ banking data to third-party providers (TPPs). It is used to drive innovation and competition within the financial services industry and to provide customers with greater ownership of their data and its use. Banks can only share customer data with third parties when the customer has given explicit consent to third parties having access to their data.
We recently dived into some interesting Open Banking use cases, if you want some real-world examples of how it’s impacting the financial services industry and its customers. Headline examples include a range of personal and business uses, from budgeting apps, savings apps, and personalized banking services to cash flow management, direct account payments, and market insights.
Banks and third parties also using the insights available through Open Banking for fraud detection. With Juniper Research recently projecting that fraud will cost global financial institutions $58.3 billion by 2030, Open Banking fraud fighting is a key use case in this evolving market.
How does Open Banking actually work?
Open Banking’s consent-driven data access model works thanks to APIs. Open Banking APIs provide the ability for data to flow securely between banks and third parties. This means that Open Banking API security is crucial to keeping customer data safe and preventing data breach issues and other cybersecurity problems.
Want a more detailed dive into what Open Banking APIs are? Then check out this article.
Key to keeping Open Banking accounts secure is authentication and authorization. To access the Open Banking API (once the customer has provided consent), the third-party must authenticate and be authorized to proceed.
This digital security process is handled via multiple components in compliant architectures. These usually include:
· An authorization server/identity provider (IdP), which can handle OAuth2 client authentication, token issuance, consent flows, and OpenID Connect user authentication.
· An API Gateway, handling token validation, mTLS enforcement, rate limiting, routing, JWS signature checks, and the like.
· A backend resource server to handle business logic, fine-grained authorization decisions, and auditing.
Once the third-party provider has been authenticated, the bank will share encrypted data with it. The third-party can then use that data to provide services to the customer. Both the bank and the third-party provider must comply with all relevant data privacy and Open Banking regulation requirements throughout this process. This is to protect customer data and prevent unauthorized access to it.
Customers have the right to revoke their consent to data sharing at any time and to manage access to it in a way that leaves them in full control.
The ecosystem roles you need to know
As we explored in this article on the evolution of financial services, Open Banking has given rise to several key ecosystem roles. It’s helpful to understand these before we move on to discussing Open Banking and security.
· Account Servicing Payment Service Provider (ASPSP): This is the bank or financial institution that holds the customer’s account. This is the party responsible for providing secure Open Banking APIs to enable access to the data it holds.
· Account Information Service Provider (AISP): This is a third-party provider that accesses the customer’s account data and uses it to provide services (such as budgeting apps).
· Payment Initiation Service Provider (PISP): This is a TPP that initiates payments on behalf of the user, often cutting out the use of traditional card networks to keep costs lower.
· Third-Party Provider (TPP): This is a collective term that encompasses both AISPs and PISPs. This is the party the bank will transmit data to via an Open Banking API.
Top Open Banking security threats and vulnerabilities
With Open Banking and security in mind, it’s important to understand the top security threats that banks and TPPs face – because understanding where they are vulnerable is key to shoring up defenses. It’s also important to appreciate the ongoing nature of such defense, as a new threat or vulnerability can arise at any time.
Within that context, let’s look at some of the most common Open Banking security issues.
| Threat or vulnerability | How it happens | Why it’s dangerous | Mitigation measures |
| Broken authentication and authorization | Exploiting weak OAuth 2.0 implementations, flawed token validation, insecure session management, or broken consent flows. | Attackers can impersonate users, escalate privileges, or access sensitive data without proper authorization. | Enforce strong token validation, implement short-lived access tokens, require multi-factor authentication (MFA), and regularly review role-based access controls. |
| API injection and abuse | Sending malicious input (SQL, NoSQL, XML, or command injection) or sending unexpected requests to manipulate backend logic. | Can lead to data corruption, leakage, remote code execution, or denial of service (DoS). | Apply strict input validation, use parameterized queries, sanitize user input, and implement Web Application Firewalls (WAFs). |
| Credential stuffing / Account takeover (ATO) | Using leaked credentials from other breaches to gain access to accounts via APIs. | Unauthorized access can result in data theft, financial fraud, or identity compromise. | Enforce MFA, implement rate limiting and account lockouts after multiple failed attempts, monitor for suspicious login patterns. |
| Third-party provider compromise | Exploiting a vulnerability in a connected third-party service (e.g. a fintech app using a bank’s API). | Treats TPPs as a supply chain risk; a compromised TPP can access user data or perform transactions. | Apply least-privilege access, conduct regular security assessments of TPPs, monitor third-party activity, and require contractual security obligations. |
| Unsecured endpoints/shadow APIs | Undocumented or forgotten endpoints left accessible without authentication or proper security controls. | Provides attackers with hidden backdoors or attack surfaces you don’t monitor. | Maintain an updated API inventory, enforce authentication and authorization on all endpoints, and regularly scan for shadow APIs. |
| Consent phishing/social engineering | Tricking users into granting broad or malicious API permissions (OAuth consent screens, fake apps). | Attackers gain elevated privileges or access to sensitive data under legitimate-looking consent. | Educate users on consent screens, implement granular scopes, monitor for abnormal permission grants, and revoke unused or excessive tokens. |
| Data leakage in transit | Failing to enforce strong encryption (e.g. TLS, mTLS) or misconfiguring certificates. | Attackers can intercept sensitive data, perform man-in-the-middle attacks, or steal credentials. | Enforce TLS 1.2+ or mTLS for all API traffic, regularly rotate certificates, and disable weak cipher suites. |
| Excessive data exposure | APIs returning more data than necessary, often due to poor filtering or serialization. | Attackers can access sensitive fields, internal IDs, or business logic. | Implement strict output filtering, adhere to the principle of least privilege, and validate responses before exposing data externally. |
| Rate limiting/DoS abuse | APIs without throttling can be overwhelmed by automated requests. | Can lead to service downtime or degraded performance for legitimate users. | Apply rate limiting, request quotas, throttling, and anomaly detection to identify abusive traffic patterns. |
| Insufficient logging/monitoring | Lack of detailed logs or delayed alerting on API activity. | Breaches or attacks may go undetected for long periods, increasing damage. | Implement centralized logging, real-time alerting for suspicious activities, and regular audits of API access logs. |
| Security misconfiguration | Default credentials, overly permissive Cross-Origin Resource Sharing (CORS) policies, or exposing sensitive headers. | Attackers can bypass security controls or pivot to other parts of the system. | Harden configurations, remove default credentials, enforce strict CORS policies, and conduct periodic automated security scans. |
Implementing measures such as those provided above to mitigate each threat or vulnerability is essential for robust, seamless, and resilient Open Banking API security. They therefore form an essential part of the risk management processes of any regulated financial institution.
Case studies in security failures: Learning from real-world incidents
No bank wants a security failure, let alone a headline-hitting one. But this is the risk that financial institutions face if they don’t secure their APIs and safeguard customer data. HSBC, Barclays, and Lloyds have already liaised with the UK’s Competition and Markets Authority in relation to incorrect information shared through their Open Banking APIs. While these were more compliance/data handling errors than security incidents, the growing use of Open Banking APIs means the need to safeguard customer data and ensure access is only by trusted and authorized parties remains paramount.
The three pillars of a bulletproof Open Banking security strategy
Ready to ensure your financial institution is doing all it can to prevent Open Banking fraud and keep user data safe? Then form your Open Banking API security strategy around three pillars:
· Regulation and standards
· An API-first approach
· A zero trust posture
Pillar 1: Regulation and standards as a security floor
Regulatory compliance isn’t some future final destination to strive for. It’s the mandatory, non-negotiable starting point for your Open Banking security strategy. Thankfully, regulators do much to help standardize Open Banking API security.
The regulatory framework and standards that apply depend on your location.
| Regime/ standard | Strong Customer Authentication (SCA)/ authentication requirements | Consent management | API security/ protocols | Other security implications/ risks |
| PSD2 (EU) | Two-factor authentication. Exemptions possible for low-risk transactions. | Implicit in payment initiation: user must authorize payments. Consent for TPP access to account info or payment initiation. | “Common and secure communication” via regulatory standards. TLS and secure channels mandated. | Friction vs usability trade-off. Complexity in implementing SCA across all flows. Operational coordination needed among banks and TPPs. |
| FAPI (global) | Strong customer authentication (multi-factor) typical in financial flows. | Fine-grained consent: clients request specific scopes; transactional consent possible. | OAuth 2.0 + OIDC hardened profile. Signed request objects (JWT). Mutual TLS (mTLS) or client certificates. Sender-bound tokens and token binding to prevent replay. | Complex to implement (certificate management, token binding). Requires secure key storage. Misconfiguration can lead to subtle security vulnerabilities. |
| CDR (Australia) | Strong authentication required for API access; aligned with FAPI-style security. | Explicit consent: scope, usage, duration defined; revocable by consumer. | Common Data Standards define API security. Uses mTLS, OAuth flows, consent tokens. | Risk of poor data quality. Accreditation requirement reduces risk but third-party risk remains. Implementation complexity for participants. |
| Section 1033/ CFPB (USA) | Secure access via portal/interface; MFA recommended. | Consumers authorize data sharing; data usage limits/purpose must be disclosed. | “Developer interface” required for data providers. Security program required (GLBA Safeguards or equivalent). | Rule does not mandate a specific technical standard; security may vary. Risk of weak third-party security. Liability and fragmentation concerns. |
| Financial Data Exchange (FDX) | Often aligned with FAPI; supports MFA/ strong authentication depending on implementation. | Consent-first: scopes, purpose, revocation enforced. | OAuth-based API flows; many implementations compatible with FAPI. | Voluntary standard: adoption and security posture may vary. Weak implementations possible if not following FAPI rigor. |
Pillar 2: Fortifying the technical core with an API-first approach
The technical core is the first essential element of a robust Open Banking and security approach. Next comes embedding an API-first strategy to fortify that technical core. This product-centric mindset underpins the creation of an API platform that supports agility and innovation, as well as faster time to market. It delivers benefits to customers and the business as a whole – much as Open Banking is intended to do.
For an example of this approach in action, you can watch Randolph-Brooks Federal Credit Union (RBFCU) explain how it built an API-first platform with FDX to benefit its members. This presentation was delivered as part of the 2025 LEAPxFinance conference, where leaders from banking, fintech, and insurance came together to explore how APIs and AI are reshaping financial services. You can watch LEAPxFinance on demand for free at your convenience.
With APIs being fundamental to Open Banking, API security is at the heart of any successful strategy. This means you’ll need your API-first approach to encompass standardized policies and technical details, from authentication to encryption.
On the authentication and authorization front, open standards play a critical role in supporting both robust security and interoperability. OAuth 2.0 and OpenID Connect (OIDC) are the standards you need. You’ll also need to pay close attention to ensuring proper scope and delivering consent management to safeguard customer data.
For encryption, you need to encrypt the data from end-to-end, so that it’s protected both in transit and at rest. That means you’ll need TLS at the transport layer and mTLS for server-to-server authentication.
API gateways prove their worth here. A gateway provides a central enforcement point for security policies, enabling you to implement rate limiting, quotas, IP allow-listing, request validation, and much more. You can also implement tokenization and manage tokens through the gateway.
Another key element of a successful Open Banking security strategy is data minimization. This is the practice of never exposing raw sensitive data (such as account numbers) and only sharing the absolute minimum required for a service to function.
Pillar 3: Adopting a proactive, zero trust posture
Another element of API security excellence – and therefore of a successful Open Banking and security approach – is a zero trust mindset. The essence of this is to never trust and always verify. That means you must authenticate and authorize every API call, whether internal or external. There is no such thing as a trusted call.
An important part of a zero trust posture is continuous monitoring and anomaly detection. You can achieve this by using real-time logging and AI and machine learning tools to detect unusual patterns, such as a user suddenly accessing data from two continents. This can significantly reduce instances of Open Banking fraud.
Part of a secure software development lifecycle is shifting security left by integrating automated security testing and code reviews into the development process. This is a fundamental part of modern API security management, as we discuss further in this insightful article.
Also crucial is comprehensive TPP vetting. You’ll need to establish a rigorous onboarding and continuous monitoring process for all third-party partners to ensure that, when they connect to your Open Banking API and integrate with your services, your security protections remain solid.
The 10-point Open Banking security checklist for your business
In need of a quick aide memoire? Use this checklist as the basis for your Open Banking API security fundamentals:
1. Adopt the FAPI security profile for all Open Banking APIs.
2. Implement multi-factor SCA for all sensitive operations.
3. Enforce mTLS to authenticate TPPs connecting to your systems.
4. Establish a formal TPP due diligence and risk assessment program.
5. Deploy an API Gateway to enforce rate limits and block malicious traffic.
6. Centralize and actively monitor all API logs for suspicious activity.
7. Conduct regular, independent penetration tests focused on your API endpoints.
8. Design and implement a clear, granular, and auditable user consent dashboard.
9. Develop and test an incident response plan specifically for an API breach scenario.
10. Continually assess and monitor with a zero trust mindset.
The future is open: Securing the next generation of finance
Open Banking is just the start. It is now evolving beyond bank-held data to include a wider range of financial information. This is enabling interoperable data-sharing across the financial sector, with Open Finance encompassing assets like investments, pensions, insurance, credit, and more.
This evolution means the attack surface is expanding to all these areas. AI and machine learning can help, moving security from reactive blocking to predictive threat intelligence. Add decentralized identity to this and new identity models could give users even more security and transparent control over their data.
Conclusion: Security as a competitive advantage
Is Open Banking safe? Yes, when implemented with the above in mind, but it requires constant vigilance as new threats and vulnerabilities emerge. Done well, you can turn Open Banking and security into a competitive advantage. Speak to the Tyk team about doing so.