Team System Security Flaws Explained 2026

Hello everyone 👋
I want to share two interesting security vulnerabilities I discovered while performing an external security assessment on a Team Management system. Both bugs were very exciting from a logic flaw and exploitation perspective 😄
These issues highlight how small design mistakes can lead to full account compromise and hidden privilege persistence.

🛑 Vulnerability #1 - Account Takeover via Predictable Reset Token + Race Condition​

While testing the Forgot Password functionality, I noticed something unusual in the password reset link: https://target.com/reset-password/4f8c2a91e7b/25
The interesting part was the last number 👀
It was clearly incremental: 25 → 26 → 27 → ...
This immediately raised a red flag 🚩
It suggested that part of the reset mechanism was predictable.

🔍 What was the real issue?​

After deeper testing, I discovered that the reset token was not properly bound to the user’s email ❌
This means:

• A token generated for one user could potentially work for another user
• The reset system lacked proper identity validation

This is a critical logic design flaw in authentication flows

🧠 Exploitation technique - Race Condition attack​

I used a Race Condition attack using Burp Suite to exploit this behavior.

Attack steps:​

1. Triggered a Forgot Password request
2. Sent the request to Repeater
3. Prepared two requests:
   • One for my email
   • One for the victim’s email
4. Sent both requests almost simultaneously using:
   • Burp Suite Group Send
   • or Turbo Intruder ⚡

💥 Result of the attack​

The system generated reset tokens in a predictable sequence, and because the token was not properly tied to a specific email:

👉 I was able to reuse or predict a valid reset token
👉 Eventually, I gained full control of the victim’s account 🔥​

💥 Root Cause Analysis​

This vulnerability happened due to:

• Predictable reset identifier generation
• Reset token not bound to user identity (email/session)
• Race condition in token generation logic

This combination made the authentication flow completely unsafe 🚨

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🛑 Vulnerability #2 - Hidden Admin Persistence via Business Logic Flaw​

The second issue was even more interesting from a business logic perspective 👀
The system was built around a Team Management structure with roles like:

• Owner → highest privileges
• Admin → lower privileges than Owner

Everything looked normal at first.

🧪 What I tested​

The Owner invited an Admin normally, and then I started testing edge cases in email modification behavior:
I tried using different character transformations:

• Unicode characters
• Greek letters
• Special symbols

Most attempts failed ❌

But one specific transformation worked: a → à
👀 This small change triggered a serious inconsistency.

⚠️ The actual problem​

After modifying the email using this character:

• The Owner removed the Admin from the team
• From the Owner’s perspective, everything looked correct
• The user disappeared from the UI completely

BUT… 😅

From the Admin’s side:
❌ They were still part of the team internally
❌ They retained partial administrative privileges
❌ They could still:

• Send invites
• Delete invitations
• Interact with admin-level actions

Even though they were completely hidden from the UI

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👻 Ghost Admin scenario​

This resulted in what can be described as:

A Ghost Admin still existing inside the system

Invisible in the interface, but still partially functional in the backend 💀

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💥 Root Cause​

The issue was likely caused by:

• Improper email normalization (Unicode / character mapping issues)
• Weak validation of user identity in team membership logic
• Broken synchronization between UI state and backend permissions

This created a desync between what the system shows and what actually exists

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🧠 Final Thoughts​

These two vulnerabilities show how dangerous logic flaws can be compared to traditional technical bugs.

• One leads to full Account Takeover 🔥
• The other leads to hidden privilege persistence 👻

Both highlight the importance of:

• Secure authentication design
• Proper input normalization
• Strong consistency between frontend and backend logic