Course

In this challenge, we delve into Extensible Stylesheet Language (XSL) and how it can be used to trigger unexpected behaviors in applications that utilize it, particularly focusing on a PHP application. We will explore how to achieve command execution by leveraging the native PHP functions enabled within the XSLT processor. By registering PHP functions in the XSLT processor, any PHP function can be called via an XSL file, making it possible to execute potentially dangerous commands.

We start by understanding how an XSLT processor works and how it can transform XML documents using XSL stylesheets. The challenge involves creating an XSL file that calls a PHP function, allowing command execution. By carefully crafting the XSL file to call a function like `phpinfo()` or any command-execution function, we can manipulate the PHP application to run arbitrary commands. This exercise highlights the importance of securely handling XSLT processors and the risks associated with enabling PHP functions within them.