How do you prevent cross-site scripting and request forgery attacks?

To prevent cross-site scripting (XSS), sanitize user input, use secure output encoding, and implement Content Security Policy (CSP). To prevent request forgery attacks, use CSRF tokens, employ same-site cookies, and implement anti-CSRF measures like middleware or built-in protections in frameworks.

Cross-Site Scripting (XSS) is a web security threat where attackers inject malicious scripts into web pages viewed by other users. There are three main types: Stored XSS (persistent), where the script is permanently stored on the server; Reflected XSS (non-persistent), where the script is included in the response dynamically; and DOM-based XSS, where client-side scripts manipulate the Document Object Model. Consequences include stealing user data, session hijacking, and spreading malware. Prevention involves validating and sanitizing user inputs, implementing secure coding practices, and using mechanisms like Content Security Policy (CSP).

Cross-Site Scripting (XSS) occurs when attackers manipulate a website to inject their own malicious script into the content delivered to end-users. Essentially, it exploits the trust a user has for a particular site, turning benign webpages into vehicles for malware dissemination. As script commands are executed as though they are part of the site's original code, they can hijack user sessions or deface websites. As someone deeply invested in web security, I find XSS a fascinating intersection of content trust issues and the need for stringent input sanitisation on the web developer's part.

Prevent XSS by validating input (rejecting malicious characters) and encoding output (convert to safe formats like HTML entities). Implement Content Security Policy (CSP) to restrict script sources. Use HTTP-only Cookies to protect session data. Escape user-generated content with encoding functions. Regularly audit for vulnerabilities, employ secure frameworks, and educate developers on best practices. This multi-layered approach fortifies web applications, ensuring robust protection against XSS attacks.

In preventing XSS, input sanitisation is paramount. Beyond validation, using libraries such as OWASP's AntiSamy or the HTML Purifier ensures only clean, safe content is rendered. Leveraging CSP is crucial but implement whitelisting of trusted domains rather than blanket policies. In WordPress, functions like `esc_html` are my go-to for output encoding. Remember, vigilance in keeping such defences robust in the face of evolving threats is key to a secure web ecosystem.

Cross-Site Request Forgery (CSRF) is an attack where an adversary deceives an authenticated user into unknowingly executing undesired actions on a web application. The attacker typically crafts a malicious link, image, or form that triggers a forged request to the targeted server, exploiting the user's existing authentication. This could lead to unauthorized actions, such as altering passwords, initiating fund transfers, or deleting data. CSRF attacks leverage the trust established between a user and a web application, emphasizing the importance of implementing protective measures like anti-CSRF tokens to validate legitimate requests and thwart unauthorized actions.

Prevent CSRF with anti-CSRF tokens—unique values attached to each authenticated request. The server validates tokens against those stored in the user's session or cookie. SameSite cookies hinder cross-origin requests, and a strict Referrer Policy minimizes data exposure. Custom headers and server-side validation add extra protection. Utilize double-submit cookies, generating tokens in both cookies and hidden form fields for heightened security. Designate appropriate HTTP methods, favoring POST for impactful actions. These strategies collectively fortify applications, thwarting CSRF attempts and safeguarding user interactions.

Test for web attacks using tools like OWASP ZAP, Burp Suite, and Nmap for automated scans. Employ browser developer tools and proxies for manual testing, inspecting code and modifying requests. Conduct penetration testing with ethical hackers to simulate real-world attacks. Utilize static analysis tools (e.g., Bandit) for source code examination and dynamic analysis tools for runtime behavior monitoring. Stay informed on vulnerabilities through databases like NVD and security headers. Regular security audits, combining automated and manual testing, are vital for ongoing protection against evolving threats.