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Secure Coding Patterns

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Security engineers are often asked to review code and identify risky patterns. Interviews test your ability to spot vulnerabilities, reason about their impact, and propose practical fixes

What to expect

Typical interview prompts include:

  • “You’re reviewing code for an API endpoint that processes user input. What do you look for?”
  • “Here’s a function handling authentication. Are there any vulnerabilities?”
  • “Which patterns in this snippet could lead to injection or data leaks?”

The majority of questions on secure coding patterns are scenario-based.

Interviewers want to see that you can reason systematically, not just identify specific vulnerabilities by name.

How to answer

Use this three-step process to explain your reasoning clearly:

  1. Identify risky patterns (anti-patterns). “I look for unsafe input handling, missing validation, or direct database queries.”
  2. Explain the risk. “This could allow attackers to inject code or access unintended data.”
  3. Propose a fix. “Use parameterized queries and validate input before executing database calls.”

Secure code cheatsheet

The table below summarizes common insecure coding patterns, the risks they create, and recommended mitigations. This helps you reason quickly and provide actionable advice during interviews.

AreaSecure patternAnti-patternRisk
Input validationValidate and sanitize all input on the server side.Accept unvalidated input from users or clients.Injection, buffer overflow.
AuthenticationCentralized authentication with short-lived tokens.Custom-built authentication logic or missing session expiration.Credential reuse, session fixation.
AuthorizationEnforce access control on the server side.Rely on client-side checks or hidden UI elements.Privilege escalation.
Data protectionEncrypt sensitive fields before storage.Store plaintext passwords or secrets in config files.Data exposure.
Error handlingReturn generic error messages.Display stack traces or system details.Information disclosure.
LoggingLog security events with proper redaction.Log PII or secrets in plaintext.Privacy and compliance violations.

Prompt: “You’re reviewing code for an API endpoint that processes user input. What do you look for?”

Strong structured response:

  1. Check for input validation and output encoding to prevent injection or XSS.
  2. Review authorization logic to ensure users can only modify their own data.
  3. Ensure error handling avoids leaking details about system internals.
  4. Verify logging practices redact sensitive input and output fields.
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