[NEW] React Security Best Practices

Common React Security Vulnerabilities (30%): Deep dives into Cross-Site Scripting (XSS) prevention within the virtual DOM, CSRF protection strategies, and the unique security considerations of Server-Side Rendering (SSR).

Security Features and Best Practices (30%): Managing secure dependencies, implementing robust authentication and authorization flows, and executing secure deployment and hosting strategies.

B. Using a library like DOMPurify to sanitize the string before passing it to dangerouslySetInnerHTML.

C. Wrapping the raw string in a <div> tag.

D. Using JSON.stringify() on the HTML content before rendering.

E. Storing the HTML in the component's state without any modifications.

F. Disabling the Virtual DOM for that specific component.

Correct Answer: B

Explanation:

A (Incorrect): Passing raw, unsanitized strings directly to this property is the primary cause of XSS vulnerabilities in React.

C (Incorrect): Simply wrapping text in a <div> does not prevent the browser from executing script tags within that text if it is rendered as HTML.

D (Incorrect): This would display the stringified JSON text on the screen rather than rendering the intended HTML.

E (Incorrect): State storage doesn't provide security; the vulnerability occurs at the point of rendering.

F (Incorrect): You cannot "disable" the virtual DOM in this manner, and doing so wouldn't solve the underlying injection risk.

Question 2: When implementing Server-Side Rendering (SSR) with React, what is a critical security risk associated with "dehydrating" the initial state?

B. High CPU usage on the client's browser.

C. Data being "scraped" by search engine bots.

D. Sensitive data or secrets being exposed in the window.__PRELOADED_STATE__ global variable.

E. The hydration process slowing down the initial paint.

F. Incompatibility with older versions of Node.js.

Correct Answer: D

Explanation:

A (Incorrect): This is a styling issue, not a core security vulnerability.

B (Incorrect): SSR generally reduces client-side CPU load by delivering a pre-rendered page.

C (Incorrect): While true, this is a privacy/SEO concern rather than an application security vulnerability.

E (Incorrect): This is a performance concern (Total Blocking Time), not a security threat.

F (Incorrect): This is a development environment requirement.

Question 3: How does React's default behavior help protect developers from Cross-Site Scripting (XSS) by default?

B. By escaping all values embedded in JSX before rendering them.

C. By requiring a password to use the useState hook.

D. By blocking all external API requests.

E. By force-refreshing the browser every 5 minutes.

F. By only allowing the app to run on localhost.

Correct Answer: B

Explanation:

A (Incorrect): React does not perform encryption on state variables.

C (Incorrect): React hooks do not have authentication requirements.

D (Incorrect): React does not restrict network traffic; that is the responsibility of CSP or browser policies.

E (Incorrect): This would be a terrible user experience and provides no security value.

F (Incorrect): React is designed to be deployed to production web servers globally.

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