Cross Site Scripting (XSS)

Description

Cross-Site Scripting attacks are a type of injection problem, in which malicious scripts are injected into the trusted web sites. Cross-site scripting (XSS) attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user.

An attacker can use XSS to send a malicious script to an unsuspecting user. The end user’s browser has no way to know that the script should not be trusted, and will execute the script. Because it thinks the script came from a trusted source, the malicious script can access any cookies, session tokens, or other sensitive information retained by your browser and used with that site. These scripts can even rewrite the content of the HTML page.

See How to Fix it!

Risk

The malicious result can be obtained by XSS are:

• Identity theft
• Accessing sensitive or restricted information
• Gaining free access to otherwise paid for content
• Spying on user’s web browsing habits
• Altering browser functionality
• Public defamation of an individual or corporation
• Web application defacement
• Denial of Service attacks

How To Prevent XSS

Prevent XSS in ASP.NET
Prevent XSS in JAVA
Prevent XSS in PHP

References

https://www.owasp.org/index.php/Cross-site_Scripting_%28XSS%29
http://en.wikipedia.org/wiki/Cross-site_scripting
https://www.owasp.org/index.php/XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet