Understanding XSS Attacks

Cross-Site Scripting (XSS) is a type of security vulnerability typically found in web applications. It allows attackers to inject malicious scripts into web pages that are viewed by other users. The scripts can be executed in the context of the user's browser, leading to unauthorized actions or data theft.

1. Stored XSS: The malicious script is stored on the server (e.g., in a database) and served to users.
2. Reflected XSS: The script is reflected off a web server, typically via a URL query parameter, and executed immediately.
3. DOM-based XSS: The vulnerability exists in the client-side code and results from modifying the DOM without proper validation.

XSS attacks occur in the following steps:

graph TD;
    A[User visits a web page] --> B{Malicious script injected?}
    B -- Yes --> C[Script stored/executed]
    B -- No --> D[Page loads normally]
    C --> E[User's browser executes script]
    E --> F[Data theft or unauthorized actions]
        

This flowchart illustrates how an XSS attack may unfold, leading to potential data compromise.

To protect against XSS attacks, consider the following methods:

• Validate and sanitize user inputs.
• Use HTTP-only cookies to prevent access to session cookies via JavaScript.
• Implement Content Security Policy (CSP) to define trusted sources for content.
• Encode data before rendering it in the browser.
• Utilize frameworks that automatically handle escaping.