Security requirements differ between Visualforce pages and Lightning Components in several key ways:
1. **HTML Encoding**: Visualforce pages automatically encode merge fields unless `escape="false"` is used or the field is in a `<script>` or `<style>` context. Lightning Components, however, do not auto-encode, so developers must manually sanitize or encode user-controlled data to prevent vulnerabilities like Cross-Site Scripting (XSS). Visualforce provides built-in encoding functions like `JSENCODE`, `HTMLENCODE`, and `URLENCODE`.
2. **Dynamic Content**: Lightning Components prohibit dynamically loading HTML, JavaScript, or CSS for AppExchange security reviews. Visualforce allows dynamic content but requires careful management to avoid risks.
3. **Namespace Isolation**: Lightning Components use LockerService for namespace isolation, preventing interference between components from different vendors. Visualforce relies on separate origins for each namespace to achieve isolation.
4. **Content Security Policy (CSP)**: Lightning Components enforce a strict CSP, blocking unsafe inline scripts and styles. Visualforce does not enforce CSP in the same way.
5. **Third-Party Resources**: Lightning Components require all scripts and styles to be included as static resources within the package. Visualforce offers more flexibility but demands careful handling to avoid vulnerabilities.
6. **Sanitization Libraries**: Lightning Components require developers to include sanitization libraries in static resources for user-controlled data. Visualforce provides built-in encoding functions.
7. **Sandboxing**: Visualforce uses unique, vendor-specific origins to sandbox JavaScript code. Lightning Components rely on LockerService for isolation, enforcing strict Content Security Policies (CSP).
8. **Component Reusability**: Lightning Components are reusable and pluggable, so developers must secure global attributes and exposed data to prevent misuse in different contexts.
These differences mean developers need to tailor their security practices to the platform they are working with.