Fintech apps are prime targets for cybercriminals due to the sensitive financial data and transactional control they offer.
This blog draws from trusted industry sources to highlight the top 10 cybersecurity threats facing fintech businesses in 2025, along with actionable steps security teams can take to strengthen their digital defences and protect users.
1. Insecure endpoints
In fintech, APIs are essential for enabling transactions, integrations, and user functionality. This heavy reliance on APIs expands the attack surface by exposing more endpoints to potential threats.
Insecure API endpoints, often resulting from missing authentication, insufficient rate limiting, or a lack of input validation, can lead to serious security incidents and data breaches. Malicious actors may exploit exposed endpoints to access sensitive data, perform unauthorised transactions, or launch denial-of-service attacks. Common issues such as exposed debug paths and unprotected test environments further increase the risk, potentially causing operational disruptions and hefty fines.
To mitigate risk, fintech teams should enforce strong authentication, apply rate limiting, validate all inputs server-side. Routinely audit APIs, deprecating unused or outdated endpoints to reduce the attack surface to close any security gaps before they’re exploited.
2. Broken access control
Broken access controls are a common vulnerability within businesses with complex user roles and can pose significant risks when in the hands of malicious actors. Broken access controls happen when a system fails to properly restrict user access, allowing unauthorised access to data or actions.
This means that user sessions can be hijacked by hackers or insider threats, allowing the illegitimate privilege escalation or access to restricted data.
The most efficient way to minimise the security risks of broken access controls is through regular monitoring of the user permissions within your workplace. Implementing the principle of least privilege, where users are granted only the minimum amount of access necessary, is also a vital way to take a proactive approach to software security. From a more technical perspective, fintech teams should prioritise securing APIs and endpoints, implement robust session management for financial transactions, and avoid hardcoded access controls that could expose sensitive account or payment data.”
3. Improper input validation
Fintech apps handle large amounts of user input. Poor input validation opens doors to injection, logic abuse, and overall system instability, jeopardising application security and risking the exploitation of confidential information.
To mitigate the risk of improper input validation, always validate and sanitise user input on the server side and never trust client-side data. Enforce strict data types, use safe-listing to define acceptable input, and normalise data to prevent injection attacks, logic flaws, and unexpected behaviour.
It’s also important to stay aware of regulatory frameworks, such as PCI-DSS, that can help your organisation address improper input validation. Following these standards can greatly assist your security team in effective vulnerability management and maintaining strong security practices.
4. Business logic flaws
Flawed workflows, such as transaction approvals, are highly exploitable but can live in your application for months without detection. Business logic flaws allow attackers to bypass critical controls (e.g., transaction limits, approval requirements, or authentication checks) by manipulating the intended workflow, enabling them to exploit weaknesses in how your fintech application handles processes and decisions.
To mitigate business logic flaws, thoroughly understand the intended workflows, implement strong access controls, and conduct rigorous manual testing alongside automated checks. Regular threat modelling, developer training, and monitoring for abnormal behaviours help minimise the risk of exploitation and misuse.
5. Insecure Continuous Integration (CI) and Continuous Deployment/Delivery (CD)configurations
Over-permissioned pipelines, leaked secrets, and unauthorised deployments are all common consequences of insecure CI/CD configurations. Fast-paced Software Developer Life-Cycles (SDLC)”, while beneficial to maintaining and improving your web applications, can inadvertently risk the integrity of your systems.
To mitigate these issues, enforce least privilege access, use “secret” management tools, and implement rigorous validation and auditing processes within your CI/CD pipelines, especially in fast-paced development environments.
6. Hardcoded secrets
Hard-coded secrets are still prevalent in fintech mobile apps, posing significant security risks. Developers often embed API keys, database credentials, or encryption keys directly in the source code for convenience. This practice exposes sensitive information to attackers, especially if the code is pushed to public or poorly secured repositories. Once accessed, these secrets can allow unauthorised entry into critical systems, leading to data breaches, financial fraud, or operational disruptions for businesses.
In fintech mobile apps, the most effective way to reduce risk is by integrating “secret” management tools and environment-specific configuration to eliminate hardcoded credentials. Developers should use secure storage solutions (e.g., Android Keystore, iOS Keychain), implement runtime secret injection, and employ automated scanning tools in the CI/CD pipeline to detect and remediate exposed secrets as part of secure coding practices.
7. Insufficient authentication and session management
Insufficient authentication and session management remain critical vulnerabilities in fintech systems. Weak multi-factor authentication, improper handling of tokens and poor session controls can allow attackers to hijack accounts or gain unauthorised access.
Common issues include short token expiry times, predictable session identifiers, failure to invalidate sessions after logout and lack of device binding.
These flaws expose users to risks such as account takeover, fraud and data theft. Fintech applications must enforce strong authentication mechanisms, secure token storage, session timeout policies and proper revocation procedures to protect users and maintain trust in their platforms. Regular penetration testing help ensure ongoing security compliance.
8. Server-side request forgery (SSRF)
Fintech apps often rely on third-party integrations to collect user data on the internet, but attackers can exploit this functionality to manipulate requests.
By crafting malicious URLs, they may trick the server into making internal calls to services not intended to be publicly accessible. This can lead to exposure of sensitive data or internal infrastructure, such as metadata services or internal APIs.
Protecting against SSRF involves strict validation of outbound requests, using allow-lists, and limiting the server’s ability to connect to internal systems. Monitoring for unusual outbound traffic patterns also helps detect potential abuse early, before it becomes a serious security issue. For example, outbound traffic should always be considered in this context to catch potential threats proactively.
9. Insecure data storage and transmission
In fintech apps, all sensitive data-especially financial and personally identifiable information (PII)- must be properly protected during storage and transmission. Without strong safeguards, this data is highly vulnerable to interception or theft, leading to compromised accounts, regulatory penalties (such as under PCI-DSS or GDPR), and erosion of customer trust.
To mitigate these risks, data should be encrypted both at rest and in transit using strong, industry-approved protocols. Additionally, secure key management practices must be enforced, and storage systems should be regularly audited for misconfigurations or weak access controls.
10. Lack of rate limiting and abuse protection on web applications
Fintech platforms risk being exposed to a broad spectrum of threats if rate limiting and abuse protection controls are not implemented. Brute-force attacks on login pages, automated credential stuffing, API scraping, and denial-of-service attempts are just a few examples of the attacks that a lack of security controls leaves organisations vulnerable to, with attackers able to quickly exploit these gaps to enact fraud or extract sensitive information at scale.
Implementing rate limiting, IP reputation checks, and behavioural analytics helps identify and block suspicious activity. API endpoints should be protected with strong authentication (such as OAuth 2.0 or mutual TLS), per-user and per-IP request quotas to prevent abuse, and continuous monitoring for unusual access patterns—such as high-frequency transaction attempts, access from atypical geolocations, or account enumeration behavior—which can signal fraud, automated attacks, or account compromise in fintech applications.
Best practice vulnerability management for fintech businesses
Overall, effective vulnerability management is critical for robust application security and should be a non-negotiable within fintech organisations. The vulnerabilities outlined above are intended to help DevOps and security teams strengthen their existing strategies and reduce the risk of exposing sensitive financial and user data.
In summary, our key recommendations for fintech businesses are to: integrate security early in the development lifecycle through secure DevOps practices, prioritise access control and secrets management, conduct regular pen testing and red teaming, treat mobile and API security as core priorities, and invest in threat modelling and secure architecture reviews. These steps lay the foundation for a more resilient and safe environment.
Let OnSecurity support your fintech organisation in achieving cybersecurity peace of mind. Check out our website for an instant and tailored quote.
