Hello! I'm Ashar Mahmood, a 23-year-old cybersecurity researcher who loves diving deep into access control flaws and broken authentication mechanisms. In this post, I'll walk you through a critical Authorization Bypass vulnerability I discovered on example.com, which allowed me to gain unauthorized access to their intranet portal, escalate privileges, and even perform full CRUD operations on sensitive organization data — all without having intranet permissions.

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The Discovery!

I was exploring the platform's extranet portal at: https://extranet.penetest.target.com, which allows standard users to register and log in. , I noticed the presence of an intranet environment by manual recon. Curiosity piqued, I tried visiting an intranet endpoint like: https://intranet.pentest.target.com in my logged in session.

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403 Forbidden

As expected, I was greeted with a 403 Forbidden error — my test user clearly had no permissions here. But something told me there might be a deeper misconfiguration at play…

The Breakthrough!

I decided to test whether the system was strictly enforcing access based on roles or merely cookie/session-bound logic. Firstly I tried the basic 403 Bypass tricks, which as expected gave me no results.

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No luck!!!

Then I checked my HTTP history, and to my surprise, I noticed that every time I visited https://intranet.example.com while logged in, the PHPSESSID was being replaced — it was different from the one used on the extranet portal. This made it clear that the session ID (PHPSESSID) alone was being used to verify access to the intranet.

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My hacking instincts kicked in, and I immediately attempted to replace the "Intranet portal's" PHPSESSID with the one from the "Extranet portal" by intercepting and modifying the request. To my surprise, the server responded with a 200 OK — and just like that, the Intranet UI loaded right in front of me.

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I immediately :

  • Opened Burp Suite > Match & Replace settings, and added a rule to:
  • Match: PHPSESSID from the intranet portal
  • Replace: PHPSESSID from the extranet session
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Match and replace

Boom! I had successfully bypassed the 403 restriction. I now had full access to the intranet portal.

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🔓 What Could I Do?

Once inside the intranet, I realized just how deep this rabbit hole went. Here's what I could do:

1. 🧑‍💼 Access Sensitive User Data

Endpoint:

https://intranet.example.com/users

I could view/edit a full list of internal user profiles — including names, email addresses, roles (like SECURITY, FINANCE, PROJECTMANAGER, etc.), and contact information.

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2. 🏢 Add New Organizations

Endpoint:

https://intranet.example.com/crmorganisatie/new

I was able to create entirely new organization entries within the CRM — filling out all fields and setting ownership to my advantage.

3. ✏️ Edit Existing Organizations

Endpoint:

https://intranet.example.com/crmorganisatie/edit?id=XYZ

This allowed me to modify any organization's data — including changing critical fields or transferring ownership, which could lock out the actual organization owner.

4. 🗑️ Delete Organizations

Endpoint:

https://intranet.example.com/crmorganisatie/delete?id=XYZ

I could delete any organization record from the CRM — and shockingly, no confirmation or validation was required.

🔥 Impact

This wasn't just a minor access issue — this was total intranet compromise.

  • Confidentiality: (C:H) — Access to sensitive internal user and organization data.
  • Integrity: (I:H) — Ability to alter or delete organizational records and ownership.
  • Availability: (A:H) — Deletion of organizations could lead to service disruption.
  • Privilege Escalation: (PR:L) — A low-privilege external user could act as an internal administrator.

Reflection

Uncovering this vulnerability taught me how critical it is to challenge assumptions. A simple cookie swap — something most would overlook — ended up unlocking access to a full internal intranet. It reinforced how important it is to test both obvious and non-obvious trust boundaries in web applications.

Key Learning

Always analyze session management with a critical eye. Even small inconsistencies between platforms (like intranet vs extranet) can lead to major authorization flaws. Watch cookies, tokens, and headers closely — the smallest detail could be your biggest lead.

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Like & drop a comment if you found this helpful — happy to answer any questions! Follow for more like this one.

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