In this challenge, we delve into the intricacies of Extensible Stylesheet Language (XSL) and its potential to trigger unexpected behaviors in applications that utilize them, specifically focusing on a PHP application. The objective is to achieve command execution by exploiting the support for one native PHP function that has been enabled. The challenge involves identifying this function, which allows a single operation that can be leveraged to execute code.
The video walkthrough demonstrates the process of retrieving the source code, identifying the file_put_contents function, and crafting a payload to write data into a file. By encoding special characters to avoid breaking the XML syntax, we manage to create a web shell. This shell can then be accessed to run any command, ultimately gaining code execution and solving the challenge.