Cross-Site Scripting (XSS)
Introduction :#
XSS is a type of security attack on websites where scammer sneaks harmful scripts into a website. These scripts can steal user data, hijack user sessions, deface websites, or perform other malicious actions.
e.g. This script could be stored by a user as comments <script>alert('XSS');</script>
XSS happens because:
Lack of Input Validation
User input isn’t properly validated or sanitized.
Websites fail to check if user input is safe, allowing harmful scripts to be entered.
- Example: A comment box accepts code like
<script>alert('Hacked!');</script>.
Failure to Sanitize Input
Even if input is checked, it might not be cleaned or escaped properly.
- Example: The site should convert
<script>to<script>to display it as text.
Rendering Unsafe Content
The site might display user input as executable code instead of text.
- Example: Displaying
<script>alert('Hacked!');</script>as code executes the script.
Improper Escaping
Special characters in user input aren't treated as text but as code.
- Example: An image tag with
<img src="x" onerror="alert('Hacked!')">can run JavaScript if the image fails to load.
Not Using Security Best Practices
The site might lack security measures like Content Security Policy (CSP) headers.
- Example: Not using CSP headers that limit what scripts can run on the page.
Imagine this situation:
You’re on a website where you can leave comments, like a blog or a forum. If the website isn’t careful, someone can leave a comment with hidden bad code instead of just plain text. When someone else views this comment, the hidden bad code can run in their web browser. This bad code can do things like steal their personal information or mess with their account settings. The harmful scripts can act like a thief, stealing your information, or they can do things you didn’t agree to, like posting messages on your behalf.
How to keep our application safe from this attack:#
To keep your application safe from Cross-Site Scripting (XSS) attacks, follow these best practices:
Input Validation: Websites should check and clean up user input to remove any harmful code before displaying it.
Encoding: When showing user input, websites should convert special characters into a format that can’t be interpreted as code.
Content Security Policy (CSP): Websites can use CSP to restrict which scripts are allowed to run, adding an extra layer of protection.
This article highlights XSS attacks, their causes (like lack of input validation), and defenses such as input validation, encoding, and CSP to enhance website security.