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Cross-Site Scripting (XSS)

1. Explain how a cross-site scripting attack works in non-technical terms.

   • Cross-site scripting (or XSS) is a method of using vulnerabilities in web applications to attack a user. Basically, a computer that interacts with the world-wide web must exchange information with it. By sneaking malicious code into those "trusted" communications, it can bypass weak security measures.

2. What are the three types of XSS attacks?

   • Reflected
   • Stored
   • DOM-based

3. If an attacker successfully exploits a XSS vulnerability, what malicious actions would they be able to perform?

   • They may be able to:
     • Impersonate or masquerade as the victim user.
     • Carry out any action that the user is able to perform.
     • Read any data that the user is able to access.
     • Capture the user's login credentials.
     • Perform virtual defacement of the web site.
     • Inject trojan functionality into the web site.

4. What are some security controls that can be implemented to prevent XSS attacks?

   • Filter input on arrival.
   • Encode data on output.
   • Use appropriate response headers.
   • Use content security policy.

Source: PortSwigger