Wednesday, April 30, 2008

Types Of Cross-site scripting attacks

XSS - Types and their users

We all know that XSS is the most common exploit to be found in any website. However, different forms of XSS have different uses, as i will cover in this post. This ranges from a simple Social Engineering opportunity to a full defacement or possibly remote admin access. The following types of XSS are defined:

Type 1 XSS
Type 2 XSS and
Type 3 XSS.

Their uses are the following:

Type 1 XSS, AKA local XSS:

This form of XSS is rarely mentioned, because it is very hard to pull off and requires knowledge of either browser exploits or local OS html files. For the first scenario, the attacker could use their website to send malicious commands to the local users vulnerable HTML files (look in /WINDOWS, there are HTML files there) that executes some command on the users system.

The second form that this attack can take is using browser exploits. Using a browser exploit, the attacker can plant an activeX script locally on the users system, which can run under local HTML priveleges(all javascripts are allowed without confirmation) and install backdoors, worms, spambots etc.

Type 2 XSS AKA non-persistant XSS:

This is the type of XSS most commonly submitted to sites like They do no harm to the site itself, and they are created when javascript can be injected into a variable that is echoed back to the user in some way. Say when you enter some text into a search bar and press submit, and the new page that is loaded has what you searched saved in the search bar. you could escape the input tag using "> then inject script. This is only useful in social engineering where you get a user, or administrator, to visit the page with the same parameters you provided to create the xss, only this time with a cookie stealer script on the page. This will execute for them, logging their cookies to a site you choose.

Type 3 XSS AKA persistant XSS:

This kind of XSS is what is mostly used against guestbooks, forums and other permanent user content pages. When this type of XSS is used it stays on the page and can be used in many ways; stealing cookies, defacing a page, and spreading(the new "XSS worm" phenomenon)

These types of XSS are completely different from each other, and all serve different purposes within hacking.

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