Broken Access Control Leads To Information Disclosure

Hello Fellow Bug Bounty Hunters And security Researchers .
This Is Abhii Mali a N008 Bug Bounty Hunter From India . This Is My First Write Up About A Vulnerability Which I Found In Private Programe (Can't Disclose Name Of Programe so call it as ) so Enjoy The Finding And If You Think I Did Any Mistake Please Forgive Me And Give Me Suggestion Via Insta And Twitter @Abhii_Mali

Vulnerability Type :
Business Logic Flaws / Broken Access Control

Let's Discuss About Logic/Working Of Application !

It Is Well Known Web Application For Travel Professionals or Businesses To Arrange Trips And Share Trips Information With Customers Or Team Members . It Has Admin User (Trip Organizer) And Team Member (Normal User) Functionality. When Admin Add An User As Team Member (Let Call It As User 2 ) In The Application, All The Trips Info Is Shared With User 2. Now User 2 Can See The Trip Information and Other Basic Details Such As Trip Duration Location etc . User 2 Also Have Functionality To Make PDF Of Trip Information [ ease For Offline Usage ].

POC Screenshot

Here, Id parameter Is Trip ID Which Is Always Same For A particular Trip And In Response URL Path Of PDF Is Shown . Vulnerability Was Lies Here .

Steps To Reproduce The Vulnerability :

1. Admin add An User As Team Member , All The Trip Information Is Shared With User 2

2. User generate PDF Of Trip And Capture The Request In Burp Suite

3. Now Admin Removed User 2 From Team Then User 2 Does Not Have Access To The Trip Information But The User 2 Have ID Of Trip So He/She Can Generate PDF Using That ID Anytime With The Help Of Request Which We Kept In Burp Repeater.

4. Whenever Admin Do Any Changes In Trip Like Location Date Time Price And Then If User 2 Generate PDF Using The Vulnerable Endpoint, New PDF Will Generate Each Time With Updated Information i.e Updated Date Time Location

In-Short :)
Generate PDF Endpoint Is Vulnerable To IDOR But Attacker Can Only Get ID Of Trip If He/She Was Previous Member Of Trip .

I Tried My Best To Explain The Issue But Still If You Are In Doubt You Can Ask Me Doubts Any Time Via Twitter And Insta.
Hope You Enjoyed This Finding !!!

13/11/2020      Reported
14/11/2020      Initial Response
16/11/2020      Considered It As Low Severity 
                And Rewarded $$$

Thank You !

~Abhii Mali (@Abhii_Mali) !!!