postMessage() II
This exercise covers how insecure calls to the JavaScript function postMessage() can be used to leak sensitive information when a listener does not filter the Origin
This course delves into the exploitation of web applications that use addEventListener() without proper origin verification. The vulnerability allows for cross-origin communication via the postMessage method, enabling attackers to manipulate the behavior of a victim's browser. Through practical steps and examples, you will learn how to create a malicious HTML page that opens the vulnerable application in an iframe and sends a crafted postMessage to exploit the vulnerability.
The course is based on content from EdOverflow's Bug Bounty Wiki and Detectify Labs, offering a comprehensive guide on how to identify and exploit this type of vulnerability. You will follow a structured approach: studying postMessage usage, creating a malicious page, baiting the victim, and finally retrieving the leaked key. Additionally, the course emphasizes the importance of checking the origin of events to prevent such vulnerabilities.