Securing your code with the XSS Sanitizer Library
Cross Site Scripting
First things first: what is XSS? Cross-Site Scripting (or XSS) is a type of security vulnerability that allows malicious users to inject harmful scripts into otherwise safe websites. These scripts often end up running in the browsers of unsuspecting users—without them ever realizing it. Let’s break it down—and then show you how to stop it.
- Step 1: Understand how XSS happens
- Imagine this scenario:
- You have a user profile page.
- Users can enter a biography.
- You store that biography in your database and show it on their public profile page.
- So far, so good. But here’s the catch:
- If your application doesn’t validate or escape that input, a malicious user can send key user data, allowing it to be hacked.
- Now, whenever someone views that profile, the script runs—annoying at best, dangerous at worst.
- Step 2: What’s the risk?
- Simple XSS: Annoying pop-ups (like infinite alerts).
- Advanced XSS: Scripts that send user data to third parties, steal cookies, or exploit other vulnerabilities in your app.
- In short: if you allow user input, store it, and display it later—you’re at risk.
- Step 3: Don’t trust user input. Ever.
- Here are the most common issues that lead to XSS:
- Input without restrictions - Users can enter long text with special characters or HTML.
- No validation or escaping - Input is stored as-is in your database.
- Direct output - The input is shown to other users without sanitization.
- Step 4: So, what should you do?
- Always sanitize user input. That means:
- Escape and/or trim user input before storing
- Trim input length and disallow suspicious patterns
- Limit what users can enter in the first place
- Step 5: Use the XSS Sanitizer
- We get it—escaping input manually isn’t fun. So we’ve built a small but powerful tool for you: the XSS Sanitizer.
- It does most of the hard work:
- Escapes dangerous characters
- Removes malicious tags
- Keeps user input safe while preserving formatting
- You can easily plug it into your DataFlex application, we’ll show you how in the next lesson.
Ready to implement the XSS Sanitizer in your applications? In the next lesson, we’ll walk you through exactly how to set it up.
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