Introduction
Every company protects their public APIs.
They add rate limits, token checks, WAF rules, and security scans.
But attackers don’t aim at your public APIs anymore.
They target the endpoints your engineers don’t remember.
The ones you built fast.
The ones hidden inside your codebase, staging servers, and CI environments.
These are Shadow Endpoints — and they are one of the most dangerous attack vectors in modern systems.
🚨 What Are Shadow Endpoints?
Shadow endpoints are:
- Old routes that were never removed
- Dev-only or test-only routes
- Temporary debugging endpoints
- Internal endpoints that leaked externally
- Admin functions exposed without protection
- Disabled features that still exist in code
These endpoints do not appear in API documentation but remain active in production.
Attackers love them because they:
- Skip authentication
- Bypass rate limits
- Expose hidden functionalities
- Provide internal system info
- Reveal database structures
- Allow direct access to sensitive data
And they exist in almost every fast-moving engineering team.
🔍 Real Example from a Security Incident We Investigated
A fintech startup had a production login rate limit of 5 attempts per minute.
Users were safe.
But inside their code, an old debug endpoint still existed:
POST /api/v1/login/raw
This endpoint:
- Skipped rate limits
- Returned raw login validation results
- Was never intended for production
- Was forgotten after a feature migration
An attacker found it through pattern testing and brute-checked 2 million credentials in 24 hours.
Their official logs showed “0 suspicious attempts” because the shadow endpoint wasn’t monitored.
This is the real danger.
🧠 Why Shadow Endpoints Happen
- Multiple teams pushing fast
- Legacy migrations
- Refactoring leaving dead code
- Dev-only flags forgotten
- CI environments exposing staging APIs
- Shared repos with old routes
Developers forget code.
Attackers don’t.
🔐 How to Detect Shadow Endpoints (Industry Approach)
✔ 1. Full Codebase Route Enumeration
Use AST analysis or grep to find every route defined.
✔ 2. Compare with API Documentation
Anything undocumented = suspicious.
✔ 3. Observe Traffic for Rare Endpoints
Any endpoint hit once per month = likely shadow.
✔ 4. Scan for Unauthenticated Endpoints
Tools don’t catch these — manual checks required.
✔ 5. Treat Staging & Dev Like Production
Shadow endpoints often leak from dev → prod pipelines.
✔ 6. Use StackLookup XSecurity Endpoint Radar
Our internal tools detect:
- Unused routes
- Unexpected API calls
- Internal-only endpoints accessed externally
- Abnormal pattern hits
🛠 Checklist to Protect Your System
- Remove legacy routes
- Add authentication middleware at the router level
- Version APIs properly
- Monitor 404 patterns
- Log hidden endpoints
- Never expose dev endpoints in production
- Document new routes at the time of creation
⚡ Conclusion
Shadow endpoints are the “doors nobody remembers”,
but they are the ones attackers check first.
Securing them means:
- Better architecture
- Safer codebase
- Fewer breaches
- Less blind trust in old code
This is the kind of insight that keeps companies safe — and this is exactly why StackLookup Labs exists.
