Certified Incident Handler (CIH) Practice Ecam

Which practice can make an organization's web server susceptible to XSS attacks?

1. Never limit the size of the input fields

2. Implement strict input validation

3. Limit cookies to HTTP only

4. Use Content Security Policy headers

The correct answer is: Never limit the size of the input fields

The practice that can make an organization's web server susceptible to XSS (Cross-Site Scripting) attacks is never limiting the size of the input fields. When input fields are unbounded, attackers can exploit this by injecting large amounts of malicious script code, which can then be executed in the context of a user's session. By allowing arbitrary lengths of input, there is an increased risk of attackers successfully embedding scripts that can manipulate web page content, hijack user sessions, or redirect users to malicious sites. In contrast to this, implementing strict input validation, limiting cookies to HTTP only, and using Content Security Policy (CSP) headers are all defensive measures designed to mitigate XSS vulnerabilities. Strict input validation serves to filter out potentially harmful input before it reaches the application logic. Limiting cookies to HTTP prevents them from being accessed via JavaScript, reducing the risk of exploitation through XSS. Content Security Policy headers provide a mechanism to restrict resources the browser is allowed to load, which helps block unauthorized scripts from running entirely. Therefore, these options represent best practices for securing web servers against XSS attacks, whereas never limiting input field sizes creates an opportunity for such attacks to occur.