From IDOR to Admin Takeover: How I Accidentally Walked Into an ATO

🔥 From IDOR to Admin Takeover: How I Accidentally Walked Into an ATO | by El Professor Qais - Freedium Milestone: 20GB Reached We’ve reached 20GB of stored data — thank you for helping us grow! Patreon Ko-fi Liberapay Close < Go to the original 🔥 From IDOR to Admin Takeover: How I Accidentally Walked Into an ATO Assalamualaikum and Hi everyone! Back again, Qais El Profesor here. Enough with introduction. Lets get started the Biggest Payout! $$$$ El Professor Qais Follow ~3 min read · March 24, 2026 (Updated: March 24, 2026) · Free: No 🧠 The Hunt Begins Bug hunting is often a mix of patience, frustration, and those rare moments where everything suddenly clicks. This story is about one of those moments. I was exploring a target on Bugcrowd, a fairly large web application with multiple subdomains. Like any hunter, I started mapping the surface area, checking endpoints, and digging into JavaScript files. That's when I found something interesting. 🔍 The First Clue: Internal API Exposure While analyzing the JS files, I stumbled upon an endpoint: /api/internal/user/InternalUser At first glance, this didn't look like something meant for public access. But curiosity wins in bug hunting. 😝 When I interacted with it, it returned sensitive internal data — including: Admin emails Usernames 💥 That's already a red flag. 😤 The Frustration Phase At this point, I had valid admin usernames and emails . But no password. And without credentials, it felt like hitting a wall. I tried multiple angles: Parameter manipulation Direct authentication attempts Token guessing Nothing worked. That's when I stepped back and thought: "What if I don't need the password at all?" 💡 The Breakthrough: Password Reset Abuse Instead of attacking login directly, I shifted focus to the password reset functionality . The endpoint looked like this: /api/public/memberauth/password/forgot/init Attempt 1: HTTP Parameter Pollution I tried a classic trick: /api/public/memberauth/password/forgot/[email protected],[email protected] The idea was simple: Maybe the system will send the reset link to both emails. But… no luck. 😑 🧪 Attempt 2: Direct Email Injection Then I tried something simpler. I replaced the victim's email with my own email : username = victim_admin_username email = [email protected] I sent the request… And the response came back: "status": "ok" 🤔 That was… suspicious. 📩 The Moment Everything Changed A few seconds later… 📥 I received a password reset email. For the admin account . 🚪 From Reset to Access I followed the reset link. Set a new password. Tried logging in… And just like that — I was inside the admin account. ⚠️ Root Cause Analysis This vulnerability was a combination of two critical issues : 1. IDOR (Information Disclosure) Internal API exposed admin emails and usernames No proper access control 2. Broken Password Reset Logic (ATO) Backend trusted user-controlled email parameter No verification that email belongs to username Allowed attacker to redirect reset link 💥 Impact This wasn't just a bug. This was a full Admin Account Takeover (ATO) . An attacker could: Access admin panel Modify system configurations View sensitive user data Potentially pivot deeper into infrastructure 🧠 Key Takeaways Never expose internal APIs without authentication Always validate ownership in password reset flows Don't trust client-supplied email parameters Small leaks (like emails) can lead to massive impact 🎯 Final Thoughts This bug taught me something important: Sometimes the fastest way in… isn't breaking the door. It's asking the system to open it for you. Connect me: X: https://x.com/wanahmadqais007 #cybersecurity #bug-bounty #idor #account-takeover #bug-bounty-writeup Reporting a Problem Sometimes we have problems displaying some Medium posts. If you have a problem that some images aren't loading - try using VPN. Probably you have problem with access to Medium CDN (or fucking Cloudflare's bot detection algorithms are blocking you).