API Penetration Testing Services for Banks and Fintech
Your APIs move money and customer data between apps, partners and core systems. One missing authorization check can let a caller read another customer’s account or redirect a payment. An API penetration test shows which of those weaknesses are real, how they could be used and what to fix first.
What an API penetration test covers
We agree the scope with you before testing starts, in writing. Typical API scopes look like this:
| API type | What we test | What you provide |
|---|---|---|
| Customer-facing APIs behind web and mobile apps | Login and token handling, access to other customers’ data, input handling | API documentation or a collection of sample calls, test accounts |
| Partner and open banking APIs | Access rules between partners, request signing, limits on what each partner can call | Partner onboarding documents, test credentials per role |
| Internal service APIs | Calls between internal systems that an attacker could reach after a first foothold | Network access agreed in the rules of engagement |
What is not covered
Load and stress testing is a separate service. So is a line-by-line review of the code behind the API: see our source code review service. Anything outside the agreed written rules is out of scope.
How we test
Testers work through the API the way an attacker would. They check how tokens are issued and checked, whether one user can reach another user’s records, whether a low-privilege role can call an administrator’s function, and how the API handles unexpected input. Each weakness is then combined with others to see how far an attacker could actually get.
We name the method in the scope and in the report, so reviewers can check the work against a public reference: OWASP ASVS and OWASP WSTG for the tests, PTES and NIST SP 800-115 for the process, and CVSS for severity.
What the report contains
Every finding is proven. We confirm each weakness and record the proof. If we cannot show it is real, it is not in the report.
One report serves three readers. Leadership gets a short summary of business risk. Engineers get the full detail to reproduce and fix each issue. Auditors and regulators get the control mapping. For what auditors usually ask to see, read our guide to penetration testing evidence for audit.
How findings map to your audit
Each finding links to the controls your reviewers use. The mapping is shown at framework level here; the report names the specific control for each finding.
| Framework | How an API finding is used |
|---|---|
| PCI DSS | Evidence for requirement 11.4 (penetration testing) where the API is in the cardholder data environment |
| ISO/IEC 27001:2022 | Evidence for technical vulnerability management and security testing controls |
| SOC 2 | Evidence for monitoring through separate evaluations |
| OWASP ASVS | The verification requirement each finding fails |
| Your regulator’s rules | Mapped in the same report, so no second report is needed |
From scoping to retest
- Scoping: a free 90-minute scoping session to agree what matters and what is in scope.
- Proposal: a scoped proposal within 24 hours of the call.
- Testing: paced around your live services, under rules agreed in writing.
- Report: report within 10 business days of testing.
- Retest: retest included, so you can show the fixes held.
We work from Jakarta (UTC+7), which shares the working day with Southeast Asia and Hong Kong and most of the day with Australia and North Asia. Meetings and reports are in English.
Testing live services safely
Payment and banking APIs run around the clock. Testing is paced so live systems keep running, and anything that could affect availability is agreed with you first.
API testing in practice
A bank’s open-banking API: we tested 27 endpoints and found a fund-diversion flaw and replayable signed requests. The bank fixed the critical chain in 4 days.
A digital bank’s payment module: we tested 23 endpoints. The critical issues were fixed in 3 days, a retest confirmed the fixes, and the module launched on the planned date.
More examples: our API security testing case study and how we approach open banking API security.
Which test do you need?
A penetration test proves what can be broken. VAPT adds the breadth of a scan with manual confirmation. A vulnerability assessment lists and ranks known weaknesses. If your risk sits in the screens users see, start with web application penetration testing. For continuous checks between tests, FOCTOS runs automated testing with people reviewing the results.
Questions about API testing
What is the difference between an API test and a web application test? A web application test works through the screens a user sees. An API test goes straight to the interfaces behind them, where apps, partners and other systems exchange data. Some APIs expose functions that no screen offers, so many teams test both.
How long does an API penetration test take? Usually 5 to 10 working days of testing. Larger scopes take longer; we agree the timeline first.
Will testing disrupt our live systems? We plan so it does not. Rules agreed in writing set what we test, when and how, and senior testers control the pace.
Can the report be used for our audit? Yes. Findings are mapped to ISO/IEC 27001:2022, SOC 2, PCI DSS and your regulator’s rules.
Do you sign an NDA? Yes. We can sign one before the scoping session.
Are you accredited? Yes. Snipeyes is a CREST Member and certified to ISO/IEC 27001:2022. We share the certificate and scope during procurement.
Start with a scoping session
Book a free scoping session to agree the scope of your API test, or request a scoped proposal if you already know what needs testing. Banks and payment companies can also read how we work with banking and financial services and fintech and digital payments.