You need some information about XSS.
You want to know what Cross-site-scripting is.
Cross site scripting (XSS) is some sort of computer vulnerability found in web applications. These vulnerabilities allow code injection by malicious users into the web pages viewed by other users.
For example: A malicious user attaches a script (e.g. an URL, an element in a form or a database inquiry) to something send to a web site. Later when the website is accessed by another user the script is transfered to the browser the user is utilizing and his computer is compromised.
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.