Episode 58: Youssef Sammouda - Client-Side & ATO War Stories

Episode 58: In this episode of Critical Thinking - Bug Bounty Podcast we finally sit down with Youssef Samouda and grill him on his various techniques for finding and exploiting client-side bugs and postMessage vulnerabilities. He shares some crazy stories about race conditions, exploiting hash change events, and leveraging scroll to text fragments. 

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Today’s Guest: https://twitter.com/samm0uda?lang=en

https://ysamm.com/

Resources:

Client-side race conditions with postMessage: 

https://ysamm.com/?p=742 

Transferable Objects

https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Transferable_objects

Every known way to get references to windows, in javascript:

https://bluepnume.medium.com/every-known-way-to-get-references-to-windows-in-javascript-223778bede2d

Youssef’s interview with BBRE

https://www.youtube.com/watch?v=MXH1HqTFNm0

Timestamps:

(00:00:00) Introduction

(00:04:27) Client-side race conditions with postMessage

(00:18:12) On Hash Change Events and Scroll To Text Fragments

(00:32:00) Finding, documenting, and reporting complex bugs

(00:37:32) PostMessage Methodology

(00:45:05) Youssef's Vuln Story

(00:53:42) Where and how to look for ATO vulns

(01:05:21) MessagePort

(01:14:37) Window frame relationships

(01:20:24) Recon and JS monitoring

(01:37:03) Client-side routing

(01:48:05) MITMProxy