SQL injection and XSS prevention in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding SQL Injection Risks

Which of the following best describes how SQL injection attacks occur?

A When the database server crashes due to high traffic

B When the user inputs are sanitized before being processed

C When the application uses encrypted connections to the database

D When user input is directly included in SQL queries without proper validation or escaping

💡 Hint

Think about how attackers can manipulate queries by inserting malicious code.

SQL injection happens when user inputs are inserted directly into SQL statements without proper handling, allowing attackers to alter the query logic.

❓ Architecture

intermediate

Designing Input Validation for XSS Prevention

Which design approach is most effective to prevent Cross-Site Scripting (XSS) attacks in a web application?

A Sanitize and encode all user inputs before rendering them in the browser

B Allow all HTML tags in user inputs to support rich text

C Store raw user inputs and sanitize only on the database side

D Disable JavaScript in the browser to prevent script execution

💡 Hint

Consider where and how user inputs are displayed in the browser.

Sanitizing and encoding user inputs before rendering prevents malicious scripts from executing in the browser, effectively stopping XSS attacks.

❓ scaling

advanced

Scaling Secure Input Validation in Distributed Systems

In a distributed web application with multiple microservices, what is the best practice to ensure consistent SQL injection and XSS prevention?

A Rely on the database engine to prevent injection and XSS

B Let each microservice implement its own input validation independently

C Implement centralized input validation and sanitization service used by all microservices

D Validate inputs only at the frontend client side

💡 Hint

Think about consistency and maintainability across services.

Centralizing input validation ensures uniform security policies and reduces duplication, making it easier to maintain and update protections.

❓ tradeoff

advanced

Tradeoffs in Using Parameterized Queries vs. ORM for SQL Injection Prevention

Which statement correctly describes a tradeoff between using parameterized queries and Object-Relational Mapping (ORM) frameworks for preventing SQL injection?

A Parameterized queries provide fine-grained control and are less abstract, but ORMs simplify development with built-in protections

B ORMs always produce faster queries than parameterized queries

C Parameterized queries cannot prevent SQL injection without additional sanitization

D ORMs require manual escaping of all inputs to prevent injection

💡 Hint

Consider control versus convenience in query building.

Parameterized queries allow precise control over SQL statements, while ORMs abstract query building and include automatic protections, but may add complexity.

❓ estimation

expert

Estimating Impact of Input Validation on System Performance

A web application adds comprehensive input validation and sanitization to prevent SQL injection and XSS. Which estimation best describes the expected impact on system performance under heavy load?

A A large increase in memory usage causing frequent crashes

B A small increase in CPU usage due to validation logic, generally negligible compared to network and database latency

C No impact at all since validation happens instantly

D A significant slowdown because validation requires database queries for every input

💡 Hint

Think about where validation happens and what resources it uses.

Input validation uses CPU cycles but is usually lightweight compared to other system operations like network calls and database queries, so performance impact is small.