XSSI (Cross-Site Script Inclusion)

👉 Overview

👀 What ?

Cross-Site Script Inclusion (XSSI) is a web security vulnerability that allows an attacker to include a script from another site, thus gaining access to sensitive data that the script can access.

🧐 Why ?

Understanding XSSI is important because it exposes the potential risks and vulnerabilities that exist within a web application. It can lead to serious security breaches, including stealing sensitive information, changing the behavior of the web application, or even taking control of the user's browser.

⛏️ How ?

To exploit XSSI, an attacker sends a malicious link to the user. Once the user clicks the link, the attacker's script is executed in the user's browser. This script can then access sensitive data that the user has access to on the targeted website. To prevent XSSI, always validate and sanitize input data, use HTTPOnly cookies, and implement Content Security Policies.

⏳ When ?

XSSI attacks have been around since the late 1990s when web applications started to become more interactive and began using scripts to improve user experience. They are still a common threat today due to the complexity of modern web applications and the difficulty in fully securing them.

⚙️ Technical Explanations

In an XSSI attack, the attacker tricks the user's browser into executing a script that the attacker controls but which is hosted on a different domain. This is typically achieved by manipulating the 'src' attribute of a script tag in the HTML of a web page, or by using JavaScript to dynamically create a script tag that points to the attacker's script. Once the script is executed, it operates within the same security context as scripts on the target site, allowing it to access cookies, session tokens, or other sensitive information. The script can then send this information back to the attacker.