How can you prepare for HTML5 security challenges?

1 Cross-Origin Resource Sharing

Cross-Origin Resource Sharing (CORS) is a mechanism that allows web browsers to request resources from different domains or origins than the one they are currently on. This can be useful for enabling web services, APIs, and mashups, but it can also pose a security risk if not implemented properly. CORS can expose sensitive data, allow unauthorized access, or enable cross-site request forgery (CSRF) attacks. To prevent these problems, you need to use CORS headers to specify which origins are allowed to access your resources, what methods and headers they can use, and how long they can cache the responses. You also need to validate the origin header and use tokens or cookies to authenticate requests.

2 Cross-Site Scripting

Cross-Site Scripting (XSS) is a type of attack that injects malicious code into a web page or application, usually through user input or output. The code can then execute in the browser of the victim and steal data, hijack sessions, or perform other actions on behalf of the attacker. HTML5 introduces new elements and attributes that can be used for XSS, such as <canvas>, <audio>, <video>, <svg>, and data-*. To prevent XSS, you need to sanitize and encode user input and output, use Content Security Policy (CSP) to restrict the sources and types of code that can run on your page, and use HTTP-only and secure cookies to protect session data.

3 Web Storage

Web Storage is a feature that allows web applications to store data locally on the user's browser, either persistently (localStorage) or temporarily (sessionStorage). This can improve the performance, functionality, and user experience of web applications, but it can also create security issues. Web Storage data can be accessed by any script on the same origin, which can lead to data leakage, tampering, or deletion. Web Storage data can also be vulnerable to XSS attacks, as mentioned above. To secure Web Storage, you need to encrypt and hash sensitive data, use HTTPS to prevent man-in-the-middle attacks, and limit the amount and duration of data stored.

4 Web Workers

Web Workers are a feature that allows web applications to run background tasks in parallel without blocking the main thread. This can improve the responsiveness, performance, and functionality of web applications, but it can also introduce security challenges. Web Workers can communicate with the main thread and other workers through messages, which can be intercepted, modified, or spoofed by malicious scripts. Web Workers can also access some web APIs, such as XMLHttpRequest, WebSocket, and IndexedDB, which can be used for malicious purposes. To secure Web Workers, you need to use HTTPS to prevent man-in-the-middle attacks, use CSP to restrict the sources and types of workers that can run on your page, and validate and sanitize the messages exchanged between workers and the main thread.