The Challenge
Financial applications have a broader attack surface than general web applications: payment flows with race condition risks, balance manipulation through API parameter tampering, multi-step transaction workflows with business logic flaws, and regulatory requirements (PCI-DSS, FCA, RBI) that mandate specific test coverage. General-purpose scanners find the obvious vulnerabilities — SQL injection in login forms, XSS in comment fields — but miss the application-specific logic flaws that allow attackers to steal money rather than data.
A FinTech pre-launch pentest has a specific urgency: vulnerabilities found before launch are fixed in development. The same vulnerability found by a customer or a regulatory body after launch triggers mandatory breach notification, potential fines, and the kind of press coverage that kills early traction. The cost differential is enormous — a week of testing before launch versus months of incident response after.
We approach FinTech pentests with particular focus on business logic vulnerabilities — the class of bugs that automated scanners completely miss because they require understanding what the application is supposed to do in order to recognize when it's doing something it shouldn't. These are also the vulnerabilities that attackers specifically look for in financial applications because they translate directly to money.
Signs You Need This
- You're launching a FinTech product and handling real money, payment cards, or user financial data
- Your regulatory environment (PCI-DSS, FCA authorization, DORA) requires documented security testing before go-live
- You're raising investment from institutional investors who require a pentest report as part of due diligence
- You're onboarding your first enterprise customer who mandates annual penetration testing
- Your application has multi-step transaction flows, balance transfers, or discount/coupon mechanisms that have never been adversarially tested
- Your engineering team built the security controls but hasn't validated them against real attack techniques
How We Approach It
Scoping & Rules of Engagement
We define the target environment (staging vs. production), test type (black box / grey box / white box), time window, in-scope URLs and API endpoints, and explicitly out-of-scope systems (payment processors, third-party KYC providers). For FinTech, we typically recommend grey-box testing — we receive test accounts at each role level and API documentation, which allows us to test business logic flows that would take days to discover through black-box reconnaissance. The scoping document becomes the authorisation letter protecting both parties.
Reconnaissance & Attack Surface Mapping
Technology fingerprinting, subdomain enumeration (finding staging environments and internal APIs exposed publicly), API endpoint discovery from JavaScript bundles and API documentation, third-party dependency mapping, and JavaScript source analysis for hardcoded credentials or internal endpoint references. We build a complete map of the application's attack surface before sending a single attack payload — this prevents missing endpoints and ensures systematic coverage rather than opportunistic testing.
Authentication & Session Management
We test MFA bypass techniques (OTP brute force windows, backup code weaknesses, SIM swap social engineering surface), session token entropy and predictability, account lockout policies and their absence or bypassability, password reset flow vulnerabilities (predictable tokens, no expiry, host header injection), OAuth/OIDC implementation errors (state parameter bypass, redirect_uri manipulation), and JWT vulnerabilities (algorithm confusion — RS256 to HS256 key confusion, "none" algorithm acceptance, weak HMAC secrets brute-forced offline).
Business Logic & Payment Flow Testing
This is the highest-value phase for FinTech and the one that requires the most domain understanding. We test: negative balance transactions and negative amount parameter manipulation in payment APIs, race conditions in concurrent withdrawal requests (two simultaneous withdrawals of the full balance), parameter tampering in checkout flows (amount manipulation, currency switching), coupon/discount code abuse (stacking non-stackable codes, generating valid codes from enumerable patterns), and transfer limit bypass through request parameter modification or workflow step skipping.
OWASP Top 10 Coverage + Full API Testing
Systematic coverage of injection (SQL, NoSQL, SSTI, command injection) across all user-controlled inputs, XSS (reflected, stored, DOM-based) in fields that render to other users, IDOR across every resource endpoint (can user A access user B's transactions by changing the transaction ID?), cryptographic failures (weak cipher suites, missing HTTPS enforcement, sensitive data in URL parameters), and security misconfiguration in HTTP response headers. Every API endpoint in scope is tested for authentication bypass — can a regular user reach admin endpoints?
Tools We Use
We use professional-grade tooling combined with extensive manual testing — automated tools find known vulnerability patterns, manual testing finds the business logic flaws unique to your application.
Common Mistakes We Prevent
- Testing only the happy path — the most valuable FinTech vulnerabilities exist in error flows, edge cases, and concurrent request handling
- Missing rate limit testing on OTP and authentication endpoints, leaving the door open for brute-force account takeover
- Treating IDOR testing as complete after checking a few resource types — in financial applications, every resource type (accounts, transactions, documents, beneficiaries) needs independent verification
- Testing authentication in isolation without testing session lifecycle — a login that's secure can be bypassed if the refresh token doesn't expire or invalidate on logout
What we typically find in FinTech: IDOR on account-to-account transfer endpoints, missing rate limits on OTP verification enabling brute force within 1000 attempts, JWT algorithm confusion allowing token forgery without the private key, and race conditions in withdrawal flows that allow double-spend when two requests arrive within a 50ms window.
What You Get
- Full penetration test report with CVSS 3.1 scored findings and proof-of-concept evidence
- Executive summary suitable for board, investor, or regulatory submission
- Technical annex with step-by-step reproduction steps for every finding, including the exact requests made
- Business logic vulnerability analysis specific to your transaction flows
- Remediation guidance with code-level fix recommendations for critical and high findings
- Free retest of all high and critical findings after your team has remediated them
- Letter of attestation for regulatory submissions or investor due diligence (on request)
Timeline & What to Expect
After the debrief, your engineering team works through remediations. Critical findings (those enabling direct financial loss) are typically fixed within 24–48 hours; high severity findings within a week. We then conduct a free retest — targeted at the specific remediated functionality — to confirm the fix is effective and hasn't introduced new issues.
Frequently Asked Questions
Do you test against production?
We strongly recommend testing against staging rather than production. A staging environment should be a production-equivalent configuration with production-equivalent data (ideally synthetic data that matches your data schema). Testing in production risks data corruption, transaction interference, and account lockouts for real users. If a production test is required for a specific reason, we define a tight time window, use dedicated test accounts, and have a direct line to your on-call engineer during testing.
How long does a pentest take?
A comprehensive FinTech web application pentest takes 7 days — 5 days of testing and 2 days of reporting. More complex applications (multiple user roles, extensive API surface, mobile app backend) may require 10 days. We scope based on the number of distinct functional areas and API endpoints, not a flat rate. A scoping call is always free and gives you an accurate timeline estimate before any commitment.
What if you find a critical vulnerability?
We notify you immediately — within hours of confirming the finding — rather than waiting for the final report. Critical vulnerabilities (those allowing direct financial loss, full account takeover, or data exfiltration) get same-day verbal notification followed by a written finding card with reproduction steps and recommended immediate mitigation. The finding is then documented in the final report. We've never withheld a critical finding until report delivery and never will.
When This Is the Right Fit
Pre-launch pentesting is the right fit for any FinTech product that handles real monetary transactions, payment card data, or regulated financial information. It's non-negotiable for PCI-DSS compliance, and increasingly expected by investors conducting technical due diligence on financial applications. The earlier in your release cycle you engage, the lower the remediation cost — findings caught in staging are fixed in a sprint; findings caught in production after customer data is involved are a crisis.
This is not the right fit if your application is purely informational with no financial transactions or if you're still in early-stage prototype development where the architecture is likely to change significantly. In those cases, engage us when you're approaching a feature-complete staging release and the core transaction flows are stable enough to test meaningfully.