What is CSRF and how do you protect against it?

Short answer: CSRF (Cross-Site Request Forgery) tricks a user into submitting unwanted requests to a trusted site. Protection: Use CSRF tokens with forms (e.g., csurf middleware in Express). Implement same-site cookies. Require authentication on sensitive endpoints.

Example code

const csurf = require('csurf'); app.use(csurf());

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.