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.

We're new to this podcasting thing, so feel free to send us any feedback here: info@criticalthinkingpodcast.io

Shoutout to YTCracker for the awesome intro music!

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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