XSLT Server Side Injection (Extensible Stylesheet Language Transformations)

👉 Overview

👀 What ?

XSLT Server Side Injection (XSSI) is a type of attack that exploits vulnerabilities in XSLT processing software, allowing the attacker to inject malicious XSLT code into a server-side application. XSLT, or Extensible Stylesheet Language Transformations, is a language used to transform XML documents into other formats such as HTML, PDF, or other XML documents.

🧐 Why ?

Understanding XSSI is important because it is a potent and versatile attack vector. An attacker who successfully exploits an XSSI vulnerability can potentially gain full control over a server, access sensitive data, disrupt services, or carry out other malicious actions. Given the widespread use of XSLT in web applications, it is crucial for developers and security professionals to understand XSSI and implement measures to prevent it.

⛏️ How ?

To mitigate XSSI, developers should validate all user input and reject any input that appears to contain XSLT code. They should also use a secure parser that does not allow the execution of arbitrary code. In addition, developers should keep their software up-to-date to protect against known vulnerabilities.

⏳ When ?

The use of XSLT dates back to the late 1990s, and vulnerabilities that allow XSSI have been known for almost as long. However, attacks exploiting these vulnerabilities have become more common in recent years as attackers have become more sophisticated and the use of XSLT has become more widespread.

⚙️ Technical Explanations

XSSI attacks exploit the fact that XSLT processors typically allow the execution of arbitrary code. An attacker can craft a malicious XSLT document that, when processed by the server, executes code that gives the attacker control over the server or allows them to carry out other malicious actions. The specifics of an XSSI attack can vary depending on the XSLT processor being used and the specifics of the server-side application.