Open Banking API Penetration Testing
Open Banking is OAuth with regulatory consequences. The flaws we find are rarely in the protocol and almost always in the consent: what it authorised, how long it lasts, and whether anyone checked it before moving money. CREST-certified testers, fixed price from £3,860, scoped in 24 hours.
- Unlimited retesting
- No rescheduling or cancellation fees
- Fixed quote within 24 hours
“I would highly recommend EJN Labs to any organisation seeking reliable, detailed, and well-managed penetration testing services, particularly for government or enterprise-level projects.”
Imran SaghirProject Lead, SquareOne“There wasn’t another company we could find that could deliver what we needed in the timeframe we needed. The client loved it, and we got instant ROI from the engagement.”
Dan WilcocksonCo-Founder, CelloriWhether you are an account information provider, a payment initiation provider or the bank on the other side, the security model rests on a consent object: which accounts, which permissions, for how long. Everything else is plumbing around that decision.
Why consent is the control that matters
What we look for is whether the consent is genuinely enforced on every call rather than checked once at authorisation. An access token that outlives its consent, a consent that can be amended after approval, or an account request that returns data outside the permissions granted are all findings we have raised.
The FAPI profile exists because plain OAuth is not sufficient here, and conformance is worth verifying rather than assuming. We pen test the profile requirements, the certificate handling, and the redirect and token binding that stop an intercepted authorisation being replayed.
ISO 27001, SOC 2, PCI DSS and Cyber Essentials Plus audits accept manual penetration test evidence. Scan-only evidence is generally insufficient.
CONSENT, FAPI + PAYMENT INITIATION
What we actually pen test on an Open Banking implementation
Manual pen testing across the consent lifecycle, FAPI conformance, mutual TLS and certificate handling, redirect security and every payment initiation path.
Consent lifecycle
Whether consent is enforced on every resource call rather than at authorisation only, expiry and revocation behaviour, amendment after approval, and whether data outside the granted permissions is retrievable.
FAPI profile conformance
Required FAPI controls checked rather than assumed: request object signing, PKCE, nonce and state handling, token binding, and whether the authorisation server accepts a request it should reject.
Mutual TLS and certificates
Client certificate validation, whether a certificate from one participant can be used by another, certificate pinning and rotation, and the eIDAS or equivalent certificate handling in your onboarding.
Redirect and authorisation security
Redirect URI validation, open redirect in the authorisation journey, app-to-app handoff on mobile, and whether an intercepted authorisation code can be exchanged by another party.
Payment initiation flows
Amount, payee and reference integrity between consent and execution, idempotency on retries, whether a payment can be initiated outside an approved consent, and multi-authorisation and bulk payment handling.
Account information and data exposure
Whether one user’s accounts can be reached with another’s token, pagination and filter abuse to reach accounts outside the consent, and what is logged that should not be.
METHODOLOGY
Open Banking API Penetration Testing: From Scope to Attestation
CREST-aligned methodology built on OWASP Web Security Testing Guide, OWASP ASVS, NIST SP 800-115, and PTES. Each finding maps to all four standards plus your specific compliance regime.
Reconnaissance
Application mapping, technology fingerprinting, content discovery, parameter enumeration, authentication-flow analysis, role-matrix construction.
Vulnerability Assessment
Authenticated and unauthenticated automated scanning across every user role, plus targeted manual checks for known weakness patterns.
Manual Exploitation
Hands-on testing by a CREST-certified pentester. Business-logic exploitation, chained vulnerabilities, privilege escalation, impact validation.
Reporting + Retest
Executive summary, technical report with CVSS scores and reproduction steps, walkthrough call, free retest after remediation, attestation letter.
CREDENTIALS
Verified Accreditations Auditors Accept
Every credential below is independently verifiable. UK procurement teams, FCA supervisors, ISO 27001 / SOC 2 auditors, and cyber insurance underwriters all recognise these standards.
GET YOUR QUOTE
Get a CREST Open Banking pen test quote in 24 hours
A fixed-price quote back in one business day, from a named CREST assessor. No sales pipeline, no chasing.
- CREST and IASME accredited. Testing your auditors and clients already recognise.
- Fast-track testing within 24 hours where required. Free retest of every fix included.
- Live findings via your client portal, not a four-week PDF.
- Fixed price from £3,500 for a single-role, single-app scope, agreed up front. Most engagements run £5,000 and up. No day-rate surprises.
Dan WilcocksonCo-Founder, CelloriUnder NDA Further named references available on a scoping call.
- We reply within one business day with a fixed-price quote from a named CREST assessor.
- You approve the scope and we book a start date, usually within 24 hours.
- Live findings land in your client portal as we test, with a free retest of every fix.
Get your fixed pen test quote in 24 hours
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COMPLIANCE READY
Reports Mapped to Every Framework
Findings are explicitly tagged to the relevant control reference. Your audit team submits the report directly without translation work.
ISO 27001:2022
Annex A.8.8 management of technical vulnerabilities plus A.5.15-5.18 and A.8.2-8.5 access control validation.
SOC 2 Type I & II
CC6 logical access, CC7 system operations, CC8 change management evidence.
PCI DSS
Requirement 11.4 application penetration testing across cardholder data environments, including ecommerce penetration testing for online retail platforms.
FCA SYSC
SYSC 4.1.1R, 6.1.1R, 13 mapped to each finding for FCA-regulated firms.
UK GDPR
Article 32 effectiveness testing, customer-data security controls, ICO-acceptable evidence.
Cyber Essentials Plus
Direct certification through our IASME body status, single-vendor delivery.
PRICING
Transparent Open Banking API Penetration Testing Pricing
Pricing depends on app complexity, user-role count, business-logic depth, and integration surface. The day count flexes; the included deliverables stay the same across all engagements.
3 to 4 testing days
Single user role, basic CRUD application, marketing website with auth. Around 5 working days from kickoff to report.
Get a fixed quote4 to 6 testing days
Multi-role SaaS, business application with payment integration. Around 8 to 12 working days from kickoff to report.
Get a fixed quote6 to 8 testing days
Multi-tenant platform, complex authorisation matrix, integration-heavy applications. Around 15 to 20 working days from kickoff to report.
Get a fixed quotePart of Technologies We Pen Test. These are examples of the stacks we publish pages for, not a complete list. If yours is not here we still test it. Related pages:
BY SECTOR
Open Banking API Penetration Testing for Your Sector
Sector-specialist scoping for UK businesses with sector-specific compliance regimes and threat models.
Fintech & FCA-Regulated
FCA SYSC, Open Banking FAPI 1.0, PSD2 SCA, payment-flow scrutiny, KYC/AML testing.
Fintech sector pageSaaS Companies
SOC 2 Type I & II evidence, multi-tenant boundaries, role escalation, customer-tenant isolation.
SaaS sector pageLaw Firms
SRA Cyber Standard, privileged data, conveyancing fraud defence, partner-tier procurement.
Law firm sector pageHealthcare
NHS DTAC, DSP Toolkit v6, UK GDPR Article 32, EHR systems, telehealth platforms.
Healthcare sector pageInsurance
FCA / PRA Operational Resilience, cyber underwriting, claims data, broker portals.
Insurance sector pagePublic Sector
CCS / G-Cloud framework, NCSC-aligned, citizen-facing services, PSN-compliance scrutiny.
Public sector pageWHY EJN LABS
What You Get From Open Banking API Penetration Testing
Six concrete differentiators competitors don’t all match.
CREST-Certified Testers, Verifiable
Every test by a CREST-certified pen tester (CRT, CCT APP, CCT INF where applicable). Verify our company status at crest-approved.org.
24-Hour Startup, Where Required
From signed scope to active testing in a single business day for incident response, audit deadlines, or regulator-driven timelines.
Live Findings, Not 4-Week PDFs
Critical issues reported during testing through your client portal. Your team remediates while testing continues.
Audit-Ready Reports
Executive summary plus full technical report with CVSS scores and explicit framework mappings (ISO 27001, SOC 2, PCI DSS, FCA SYSC).
Free Retests, Standard
Verify remediation of every finding before close-out. Letter of attestation for audit submission included. Most competitors charge £1,500-£3,000 per retest.
UK-Based CREST Testers
Every engagement performed by vetted, UK-based CREST-certified testers, matched to your needs, security clearance, and compliance scope.
FAQ
Frequently Asked
Do you test against the sandbox or production?
Usually a full-function sandbox that mirrors production, because payment initiation testing against live accounts is rarely sensible. Where production testing is required we agree strict limits, small amounts and a named window.
Are you testing conformance or security?
Security, informed by conformance. Passing the conformance suite tells you the implementation matches the specification. It does not tell you whether your consent enforcement holds when someone actively attacks it, which is the question we answer.
We are a TPP rather than a bank. Is this relevant?
Very. A third-party provider holds certificates, tokens and consents for many users at once, which makes it a high-value target. We pen test your consent storage, token handling and certificate management as well as the API surface.
Does this satisfy our FCA obligations?
It supports them. We provide manual penetration test evidence mapped to the relevant control expectations, including ISO 27001 and PCI DSS where card rails are also in play. We are not a regulatory consultancy and will tell you where an obligation needs one.
How long does an engagement take?
Three to four testing days for a single-role implementation with a sandbox, longer where you run both account information and payment initiation, multiple ASPSP integrations or a mobile app in the journey.
20+ CREST-accredited testing services in one place
Web, mobile, API, cloud, AI, infrastructure, red team. Pick the test that fits your environment.
Get a fixed price for your Open Banking implementation
Tell us your role, which flows are in scope and whether a sandbox is available. Fixed-price quote from a named CREST assessor within one business day, unlimited retesting and no cancellation fees.
