Listen to this Post
Introduction:
A recent LinkedIn Easter egg discovered by security researcher Chad Saliby hints at an unreleased feature that inadvertently exposes internal API endpoints and user metadata. This oversight could allow attackers to scrape private profile details or exploit debug information left active in production. Understanding how such hidden functionalities work and hardening your cloud and API security posture is critical to preventing data exfiltration.
Learning Objectives:
- Identify and mitigate risks from hidden “Easter egg” features in enterprise web applications.
- Use Linux and Windows commands to audit API endpoints for unintended data exposure.
- Apply cloud hardening techniques to block OSINT gathering via debug endpoints.
You Should Know:
1. Reverse-Engineering the LinkedIn Easter Egg API Call
The Easter egg triggers a hidden GraphQL query that returns profile fields normally restricted. Below is a step‑by‑step guide to simulate the request and check for similar vulnerabilities in your own apps.
Step‑by‑step guide:
- Open browser DevTools (F12) and navigate to the Network tab.
- On LinkedIn, trigger the Easter egg (e.g., clicking a hidden UI element).
- Look for a request to
https://www.linkedin.com/voyager/api/identity/profiles` with a custom headerX‑Restli‑Protocol‑Version: 2.0.0`. - Extract the response; it may contain
privateEmail,phoneNumbers, orlastLoginIp.
Linux command to test your own API for debug endpoints:
Use curl to probe for hidden GraphQL introspection
curl -X POST https://your-api.com/graphql \
-H "Content-Type: application/json" \
-d '{"query":"query { __schema { types { name fields { name } } } }"}'
Windows PowerShell alternative:
Invoke-RestMethod -Uri "https://your-api.com/graphql" -Method Post -Body '{"query":"query { __schema { types { name } } }"}' -ContentType "application/json"
Mitigation: Disable GraphQL introspection in production. Add API gateway rules to block requests with uncommon headers like X‑Restli‑Protocol‑Version.
2. OSINT Hardening Against Profile Scraping
Attackers can automate Easter‑egg endpoints to harvest thousands of profiles. This section shows how to detect and block such scraping.
Step‑by‑step guide using Linux iptables:
- Identify scraping patterns – high request rates to
/voyager/api/identity.
2. Rate‑limit suspicious IPs:
sudo iptables -A INPUT -p tcp --dport 443 -m recent --name api_abuse --set sudo iptables -A INPUT -p tcp --dport 443 -m recent --name api_abuse --update --seconds 60 --hitcount 10 -j DROP
3. Log blocked attempts:
sudo iptables -A INPUT -p tcp --dport 443 -m recent --name api_abuse --update --seconds 60 --hitcount 10 -j LOG --log-prefix "API_SCRAPE: "
Windows Defender Firewall with PowerShell:
New-NetFirewallRule -DisplayName "Block LinkedIn Scraper" -Direction Inbound -RemoteAddress 192.168.1.0/24 -Action Block Use dynamic rate limiting via Windows Filtering Platform (WFP) – requires third-party tool like `nps` or `vlmcsd`
Cloud hardening (AWS WAF):
{
"Name": "RateLimitHiddenAPI",
"Priority": 1,
"Statement": {
"RateBasedStatement": {
"Limit": 50,
"AggregateKeyType": "IP",
"ScopeDownStatement": {
"ByteMatchStatement": {
"SearchString": "/voyager/api/identity",
"FieldToMatch": { "UriPath": {} },
"TextTransformations": [],
"PositionalConstraint": "CONTAINS"
}
}
}
},
"Action": { "Block": {} }
}
3. Exploiting Debug Endpoints – A Pentester’s View
Hidden Easter eggs often leave debug endpoints active. Below is a controlled vulnerability exploitation example for educational purposes.
Step‑by‑step guide to simulate the attack:
- Enumerate subdomains for `.linkedin.com` (only in authorized labs):
sublist3r -d linkedin.com -o linkedin_subs.txt
2. Test each subdomain for common debug paths:
while read sub; do
curl -s -o /dev/null -w "%{http_code} $sub\n" https://$sub/debug/vars
done < linkedin_subs.txt
3. If `200 OK`, retrieve exposed environment variables:
curl https://debug-target.com/debug/vars | jq '.EnvVars | keys'
Linux command to dump all cookies and local storage (for testing your own browser):
Extract LinkedIn cookies from Chrome on Linux sqlite3 ~/.config/google-chrome/Default/Cookies "SELECT host_key,name,encrypted_value FROM cookies WHERE host_key LIKE '%linkedin%';"
Windows command (using certutil to decode base64 cookies from browser DB):
certutil -decode encoded_cookie.txt decoded_cookie.txt
Mitigation: Remove all /debug, /metrics, `/health` endpoints from production. Implement cookie flags HttpOnly; Secure; SameSite=Strict.
4. Automating Detection of Easter‑Egg Leaks with SIEM
Use this Sigma rule to detect unusual GraphQL queries containing `__schema` or `__type` (indicating introspection attempts).
Sigma rule (YAML):
title: GraphQL Introspection Query Detection status: experimental logsource: product: webserver category: access detection: selection: c-uri|contains|all: - 'query' - '__schema' condition: selection falsepositives: - Legitimate internal debugging level: high
Linux command to tail logs for such patterns:
tail -f /var/log/nginx/access.log | grep -E "(query.__schema|X-Restli-Protocol-Version)"
- Training Course Integration – Building a Secure API Testing Lab
To practice finding and fixing Easter‑egg vulnerabilities, set up a local lab with a deliberately vulnerable API.
Step‑by‑step lab setup on Linux:
- Install Docker and pull the vulnerable GraphQL API:
sudo apt update && sudo apt install docker.io -y sudo docker pull danielgtaylor/aglio
- Run a vulnerable API (example with introspection enabled):
sudo docker run -d -p 8080:80 --name vuln-api graphql-engine/voyager
- Use the earlier `curl` introspection command to extract schema.
4. Harden the API by disabling introspection:
Edit the GraphQL engine config
sudo docker exec -it vuln-api sh
echo '{"introspection": false}' > /app/config.json
exit
sudo docker restart vuln-api
Windows lab using WSL2:
wsl --install -d Ubuntu wsl bash -c "sudo apt update && sudo apt install docker.io -y && sudo docker run -d -p 8080:80 graphql-engine/voyager"
What Undercode Say:
- Key Takeaway 1: Hidden Easter eggs are not harmless – they often expose production debug interfaces that leak sensitive user metadata. Treat every hidden feature as a potential attack vector.
- Key Takeaway 2: Proactive API hardening, including disabling introspection, rate limiting, and strict header validation, blocks the majority of OSINT scraping attempts before they start.
Easter eggs in enterprise software represent a clash between delight and security. While engaging users, they frequently bypass standard security reviews and remain in production for years. LinkedIn’s case is a reminder that any unauthenticated or semi‑authenticated API endpoint – even one triggered by a hidden click – must undergo the same threat modeling as public endpoints. The best defense is to assume every internal endpoint will eventually be discovered and to design with zero‑trust API principles. Regular automated scanning for debug paths (
/debug,/voyager/internal) and GraphQL introspection should be part of every CI/CD pipeline. Finally, train developers to treat “secret” features as high‑risk technical debt.
Prediction:
Within the next 12 months, we will see a surge in bug bounty reports targeting Easter‑egg and “joke” features across social media platforms. Attackers will automate discovery of hidden UI triggers using browser extension fingerprinting and DOM event listeners. In response, platforms will implement strict content security policies (CSP) that block inline event handlers and obfuscate client‑side feature flags. Long‑term, AI‑driven code scanners will automatically flag any hidden functionality not explicitly documented in the public API schema, reducing the attack surface for such Easter‑egg leaks.
▶️ Related Video (80% Match):
🎯Let’s Practice For Free:
IT/Security Reporter URL:
Reported By: Chadsaliby Linkedin – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
