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hunt-fintech-graphql

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Hunt fintech-specific GraphQL vulnerabilities: money-movement mutations (transfers, redemptions, withdrawals, card top-ups), ledger/balance/portfolio query IDOR, decimal-precision and rounding abuse, idempotency-key bypass enabling double-spend, KYC/PII field-level authorization gaps, and admin-override mutations reachable via mass assignment. Distinct from hunt-graphql, which owns generic GraphQL discovery and IDOR/mutation methodology — this skill owns the delta introduced when a GraphQL layer sits in front of a ledger, wallet, payments, banking, brokerage, or lending backend, where a resolver bug moves real money instead of just leaking data. Use when hunting a fintech, banking, payments, wallet, neobank, brokerage, or lending target that exposes a GraphQL API, or when a schema/response includes balance, transfer, ledger, redeem, quote, KYC, or account-linking fields.

skills/hunt-fintech-graphql/SKILL.md

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Network or broad shell
Last checked
Nov 11, 2026

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5,527
Repository last updated
Nov 10, 2026
License
MIT

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## Why Fintech GraphQL Is a Different Risk Class

Generic GraphQL bugs (IDOR, mass assignment, introspection, batching abuse — see `hunt-graphql`)
still apply here, but the blast radius changes completely: a resolver bug in a SaaS app leaks
data, the same class of bug in a ledger mutation **moves money**. Three properties make fintech
GraphQL backends a distinct hunting surface:

- **Money-movement mutations are almost always resolvers over a double-entry ledger.** A single
  GraphQL mutation (`transferFunds`, `redeemRewards`, `withdrawToBank`) can trigger multiple
  ledger writes (debit + credit + fee) that must be atomic. GraphQL's flexible input shape and
  alias batching make it easy to desynchronize those writes.
- **Decimals are attacker-controlled input, not display formatting.** Amounts, exchange rates,
  interest, and rewards points are usually passed as GraphQL scalars (`Float`, `String`, custom
  `Decimal`/`Money` scalar). How the resolver parses and rounds that value is exploitable surface
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