Cross-Site Scripting
Web applications today rely heavily on user input, making them vulnerable to various attacks. One of the most common and dangerous among them is Cross-Site Scripting (XSS). According to the OWASP, XSS remains a critical vulnerability affecting millions of websites worldwide.
XSS attacks allow attackers to inject malicious scripts into web pages, which are then executed in the victim’s browser—often without their knowledge.
What is Cross-Site Scripting (XSS)?
Cross-Site Scripting (XSS) is a vulnerability that occurs when an application includes untrusted user input in a web page without proper validation or encoding.
Attackers inject malicious JavaScript into a website, and it runs in other users’ browsers.
How Does XSS Occur?
XSS occurs when applications:
- Accept user input (forms, comments, search fields)
- Display that input back to users
- Fail to properly validate or sanitize it
Typical Attack Flow:
- Attacker injects malicious script into input field
- Application stores or reflects the input
- Victim visits the affected page
- Malicious script executes in victim’s browser
- Attacker gains access to sensitive data
Types of XSS Attacks
1️⃣ Stored XSS (Persistent)
- Malicious script is stored in database
- Executes whenever users load the page
👉 Example: Comment section attack
2️⃣ Reflected XSS (Non-Persistent)
- Script is reflected in response immediately
- Usually via URL parameters
👉 Example: Search query attack
3️⃣ DOM-Based XSS
- Happens in browser (client-side)
- JavaScript modifies DOM insecurely
Example of XSS Attack
Input Field Injection:
Attacker enters:
What happens?
- If not sanitized, script executes in browser
- Displays alert or performs malicious actions
Advantages of XSS
These are risks, not real advantages.
- 🍪 Steal session cookies
- 👤 Hijack user accounts
- 🎣 Perform phishing attacks
- 🧠 Execute malicious scripts in user browsers
- 🔁 Redirect users to malicious websites
- 🕵️ Capture keystrokes or sensitive data
Disadvantages of XSS
- User account compromise
- Data theft and privacy violations
- Loss of customer trust
- Website defacement
- Compliance issues (GDPR, ISO 27001)
- Brand reputation damage
