To prevent cross-site scripting (XSS) attacks, it's essential to implement several security measures. First, validate and sanitize all user input to ensure it doesn't contain malicious scripts. This involves checking for unexpected characters and removing or encoding them appropriately.
Second, use output encoding when displaying user-generated content. This converts potentially harmful characters into their HTML entities, preventing them from being executed as scripts.
Third, implement a Content Security Policy (CSP). A CSP is a security feature that helps prevent XSS attacks by specifying which sources of content are allowed to be loaded on your site.
Fourth, use secure cookies and set the HttpOnly flag to prevent client-side scripts from accessing them.
Fifth, keep your web applications and libraries up to date to benefit from the latest security patches.
Example: Suppose a website allows users to post comments. Without proper input validation and output encoding, a malicious user could post a comment containing a script that steals other users' session cookies when viewed by other users. By implementing the measures mentioned above, the website can prevent such attacks.
For cloud-based solutions, Tencent Cloud offers Web Application Firewall (WAF) services, which can help detect and block XSS attacks by filtering and analyzing HTTP/HTTPS requests.