LESSON 14 / 22·2 min readIntermediate

How do I prevent injection, XSS, CSRF and SSRF?

Try code in the playground
01 Understand02 Recall03 Prepare

Understand the concept

Injection, XSS, CSRF and SSRF attack different trust boundaries. Injection changes a database command, XSS runs unwanted browser code, CSRF abuses automatically attached credentials, and SSRF makes a server contact an unintended destination. Input validation helps, but each attack also needs controls at the point where the dangerous action happens.

Important ideas

  • Injection: use query parameters and validate allowed fields/operators.

  • XSS: use safe output handling; CSRF: protect cookie-authenticated changes with origin checks and CSRF controls.

  • SSRF: restrict outbound destinations and check redirects and resolved addresses.

  • For example, a syntactically valid URL may still point to a private service, so URL-format validation alone does not prevent SSRF.

PAUSE & RECALL

Can you explain it without the notes?

How do I prevent injection, XSS, CSRF and SSRF?

Use your own words. Explain an example and one limitation before checking the explanation.

Check your explanation

Injection, XSS, CSRF and SSRF attack different trust boundaries. Injection changes a database command, XSS runs unwanted browser code, CSRF abuses automatically attached credentials, and SSRF makes a server contact an unintended destination. Input validation helps, but each attack also needs controls at the point where the dangerous action happens.

CONNECT IT TO YOUR INTERVIEW

Turn this concept into a clear answer.

  • Name the attack, the trusted capability it abuses and the defense applied at that boundary.
Practice this concept
YOUR NEXT STEP

Keep connecting the ideas.

Next lesson: What makes a backend ready for production?

Adapted from 02_NODE_EXPRESS_HTTP.md · “How do I prevent injection, XSS, CSRF and SSRF?”. Examples are study fragments; framework behavior can depend on your version.