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3-6y

Frontend Security, Auth, and Trust Boundaries

Frontend code runs in the user's browser, so it should never trust unsafe input and should never pretend it can hide secrets perfectly.

Analogy

A classroom monitor can check who enters, but the master key should still stay in the office, not under the desk.

Follow-up questions

Topic practice prompts

How do you think about token storage in frontend applications?

There is no perfect client-side answer. You choose based on threat model, UX, and server design, while keeping sensitive logic on the server.

  • Why is 'never use localStorage' too simplistic?
  • How do cookies change the CSRF discussion?
What are the main frontend security risks you mention in interviews?

XSS, unsafe HTML rendering, weak token handling assumptions, exposed client logic, and insecure third-party integrations are high-frequency frontend risks.

  • When is dangerouslySetInnerHTML acceptable?
  • What does CSP help with?
Cheat sheet

Last-day revision lines

  • Never trust raw HTML.
  • Know cookie versus token tradeoffs.
  • Use CSP as extra protection.
  • Server remains the source of truth.
Source references
  • Web performance and security: context/Web perfomance and security.docx
  • HTML CSS JS questions: context/100 important HTML, CSS, and JavaScript interview questions.pdf
Offline study support

Local resource packs for this topic

1 local packs

Use these local packs when you want broader official-source context without leaving the app.

performancePerformance and Web Vitals

Performance and Web Vitals

A local digest of high-value web performance ideas that connect directly to React and product interview rounds.

Performance and SecurityReact.jsFrontend Breadth

Web vitals, LCP thinking, responsiveness, layout stability, render cost, bundle strategy, and main-thread awareness.

Open local study pack
Next step

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