SQL Injection & Cross-Site Scripting (XSS): Exploiting Web Application Vulnerabilities

SQL Injection (SQLi) and Cross-Site Scripting (XSS) are critical web application vulnerabilities that allow attackers to manipulate databases and execute malicious scripts within user browsers. These exploits can lead to data breaches, session hijacking, and unauthorized access to sensitive information.

SQL Injection (SQLi) Attacks

What is SQL Injection?

SQL Injection is an attack where malicious SQL queries are injected into an application’s database query, allowing attackers to manipulate, extract, or delete data.

How SQL Injection Works

1. User Input Manipulation: Attackers enter malicious SQL code into input fields.
2. Query Execution: The application processes the query without proper validation.
3. Data Exposure or Manipulation: Attackers can retrieve, modify, or delete database records.

Types of SQL Injection

• Error-Based SQLi: Exploits database errors to retrieve information.
• Union-Based SQLi: Uses UNION queries to extract data.
• Blind SQLi: Executes queries without returning visible errors but still affects backend data.
• Time-Based SQLi: Measures response delays to infer database structure.

Real-World SQL Injection Examples

• Yahoo (2012): SQL Injection led to the exposure of 450,000 user credentials.
• Sony PlayStation Network (2011): Attackers compromised 77 million user accounts via SQLi.
• U.S. Voter Database Leak (2015): SQLi exploited a government website, exposing voter records.

Cross-Site Scripting (XSS) Attacks

What is XSS?

Cross-Site Scripting (XSS) is a web security vulnerability that allows attackers to inject malicious scripts into web pages, affecting users who interact with the compromised application.

How XSS Works

1. Injection: The attacker injects a malicious script into a vulnerable website.
2. Execution: The victim’s browser executes the script unknowingly.
3. Exploitation: The attacker can steal session cookies, redirect users, or deface web pages.

Types of XSS Attacks

• Stored XSS: The script is permanently stored on the server and affects all users.
• Reflected XSS: The script is immediately executed when a user clicks a malicious link.
• DOM-Based XSS: Manipulates the Document Object Model (DOM) of a website to execute scripts.

Real-World XSS Examples

• MySpace Worm (2005): Used XSS to spread rapidly across user profiles.
• British Airways Data Breach (2018): Hackers used XSS to steal payment data.
• Tesla (2020): XSS vulnerability exposed employee data but was patched before exploitation.

How to Prevent SQL Injection & XSS

Preventing SQL Injection

• Use Prepared Statements & Parameterized Queries:

  SELECT * FROM users WHERE username = ? AND password = ?

• Apply Least Privilege Principle (LPA): Limit database user permissions.
• Sanitize User Inputs: Validate and escape special characters.
• Use Web Application Firewalls (WAFs): Block SQLi attack patterns.

Preventing Cross-Site Scripting (XSS)

• Sanitize & Encode User Input: Prevent script execution by escaping HTML tags.
• Use Content Security Policy (CSP): Restrict script execution origins.
• Implement HTTP-Only & Secure Cookies: Prevent session hijacking.
• Avoid InnerHTML & Eval() in JavaScript: Prevent DOM-based XSS exploits.

SQL Injection vs. Cross-Site Scripting (XSS)

Feature	SQL Injection (SQLi)	Cross-Site Scripting (XSS)
Target	Database	Web browser
Impact	Data theft, database manipulation	Session hijacking, malicious redirects
Attack Vector	Malicious SQL queries	Injected JavaScript, HTML, or Flash
Prevention	Prepared statements, input validation	Input encoding, CSP, secure cookies

Conclusion

SQL Injection and Cross-Site Scripting (XSS) remain among the most exploited web vulnerabilities. Developers and security teams must implement secure coding practices, input validation, and modern security frameworks to protect web applications from these threats.

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