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Threat Model Analysis for facebook/react

Threat: Cross-Site Scripting (XSS) via dangerouslySetInnerHTML

  • Description: An attacker injects malicious JavaScript code into a text input field (or other data source) that is later rendered using React's dangerouslySetInnerHTML prop without proper sanitization. The attacker crafts a payload that, when rendered in the context of another user's browser, executes the attacker's script. This is a direct misuse of a React-provided feature.
    • Impact:
      • Theft of user cookies and session tokens, leading to account takeover.
      • Redirection of users to malicious websites.
      • Modification of the page content (defacement).
      • Keylogging and capturing of user input.
      • Execution of arbitrary code within the user's browser, potentially leading to further exploitation.
    • Affected Component: Any component that utilizes the dangerouslySetInnerHTML prop, specifically when handling user-supplied or untrusted data. This is a function call within a component, not the component itself.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Primary: Avoid dangerouslySetInnerHTML whenever possible. Utilize React's standard JSX rendering, which provides automatic escaping of content.
      • If Unavoidable: Always sanitize the HTML input using a robust and well-maintained sanitization library like DOMPurify before passing the content to dangerouslySetInnerHTML. Example: <div dangerouslySetInnerHTML={{ __html: DOMPurify.sanitize(props.content) }} />
      • Ensure the sanitization library (e.g., DOMPurify) is kept up-to-date with the latest security patches.
      • Implement a strong Content Security Policy (CSP) as a defense-in-depth measure to mitigate the impact of any successful XSS, even if sanitization fails.

Threat: State Exposure due to Improper Asynchronous Handling (Sensitive Data Leak)

  • Description: A React component makes an asynchronous request (e.g., fetching data or submitting a form). Before the request completes, the component temporarily stores sensitive data (like a password or API key incorrectly placed in state) in its state. If the component unmounts or re-renders before the asynchronous operation completes and clears the state, that sensitive data might remain accessible in a previous state snapshot (observable via React DevTools or network traffic analysis). This is a direct consequence of how React handles state updates and component lifecycles.
    • Impact:
      • Exposure of sensitive user data (passwords, personal information, or improperly stored API keys).
      • Potential for replay attacks if the exposed data includes authentication tokens.
    • Affected Component: Any React component that manages state and performs asynchronous operations, particularly within lifecycle methods (e.g., componentDidMount, componentDidUpdate, or event handlers like onClick with promises). The issue lies within the component's state management and asynchronous logic.
    • Risk Severity: High
    • Mitigation Strategies:
      • Use useEffect (in functional components) with proper cleanup functions to cancel any pending asynchronous operations when the component unmounts. This prevents state updates after unmounting.
      • Avoid storing sensitive data in component state for longer than absolutely necessary. Ideally, sensitive data should never be stored in client-side state.
      • Utilize a state management library (Redux, Zustand, etc.) that provides well-defined mechanisms for handling asynchronous operations and managing loading/error states, reducing the risk of race conditions.
      • Consider using a "mounted" flag or a similar mechanism to prevent state updates after a component has unmounted, as an additional safety measure.

Threat: Server-Side XSS during Server-Side Rendering (SSR)

  • Description: An attacker injects malicious JavaScript code into a text input field (or other data source). The application uses server-side rendering (SSR) with a framework like Next.js or Remix, which builds upon React. The server renders the React component, including the unsanitized user input, directly embedding the malicious script into the initial HTML sent to the client. This bypasses React's usual client-side escaping.
    • Impact: Identical to traditional XSS: cookie theft, session hijacking, website defacement, keylogging, and potentially arbitrary code execution within the user's browser. The crucial difference is that the attack occurs before React hydration on the client-side.
    • Affected Component: Any React component that is rendered on the server (using functions like getServerSideProps or getStaticProps in Next.js, or loaders in Remix) and includes user-supplied data without proper server-side sanitization. The vulnerability lies within the server-side rendering logic of the component.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Mandatory: Sanitize all user input on the server before including it in the rendered HTML. Use a robust HTML sanitization library that is specifically designed and tested for server-side use (e.g., a server-compatible version of DOMPurify).
      • Leverage the escaping mechanisms provided by the SSR framework itself (e.g., Next.js's built-in escaping functions).
      • Implement a strong Content Security Policy (CSP) to limit the impact of any successful XSS, even if server-side sanitization fails. This is a crucial defense-in-depth measure.

Threat: Insecure Direct Object Reference (IDOR) Exploiting Component Prop Handling

  • Description: A React component receives an ID (or other identifier) as a prop, and it uses this ID to fetch data from an API without performing adequate server-side authorization checks. An attacker modifies this prop (e.g., by manipulating the URL or using browser developer tools) to an ID they are not authorized to access. The server, lacking proper checks, returns the sensitive data associated with the attacker-supplied ID. While IDOR is not exclusive to React, the common pattern of passing IDs as props makes it a relevant concern.
    • Impact:
      • Unauthorized access to sensitive data belonging to other users.
      • Potential for data modification or deletion if the API allows write operations based on the manipulated ID.
    • Affected Component: Any React component that receives an ID (or similar identifier) as a prop and uses that ID to fetch or manipulate data without relying on robust server-side authorization. The vulnerability is primarily on the server-side, but the component's prop handling is the attack vector.
    • Risk Severity: High
    • Mitigation Strategies:
      • Crucial: Implement robust server-side authorization checks. The server must verify that the currently authenticated user has the necessary permissions to access the resource identified by the ID, regardless of how that ID was provided to the client.
      • Avoid using predictable or sequential IDs for sensitive resources.
      • Use UUIDs or other cryptographically secure identifiers.
      • Never rely solely on client-side validation or checks for authorization. Client-side logic can be bypassed.