With the advancement of applications that allow websites to be built in minutes, comes the dangers of application security issues. Generally when applications are built (to build websites) the webmaster enters the information into the application that generates the website. This website then goes into production and later further Cross Site Scripting vulnerabilities are discovered therefore making it possible for the website to be hacked.
The developer of the website should always check for updates on software to prevent vulnerabilities. Vulnerabilities develop over time and whatever was developed becomes unsecure. If an update for the software is made available, the webmaster should download and install the update and replicate and replace the production website.
Most applications have security measures programmed into the application. Having a secure application is only possible during the release of the software. Always remember that software can be released today only to have a security hole within the same day! Patches and updates are important to stop cross site scripting vulnerabilities.
Webmasters and developers can take a positive stance by deploying an application firewall that controls file execution and how these applications work and interact with website visitors. Many hardware firewalls have DMZs and software / firmware that helps to prevent malicious activity. Firewalls like software need to updated on a regular basis.
XSS known as Cross Site Scripting involves the injection of code. What Code? This website (Link) gives great examples of the actual code. By studying this code, a webmaster can get a thorough understanding of the code that can be injected. Without viewing this site negatively, it is a great learning tool. This site is referenced on OWASP. Open Source Security Applications can help with protection of websites (See my past article).