And this lecture and the next few lectures we're going to talk about a vulnerability called excesses
excesses is short for a cross site scripting this type of vulnerability allows an attacker to inject
javascript into a page so javascript is a programming language.
And using this vulnerability an attacker would be able to execute code written in Javascript and to
a certain page into a Web site javascript is a client side language.
So when the code is executed it will be executed on the client on the user on the person who is browsing
the web page.
It's not going to be executed on the server.
So even if your code results into giving you a reverse shell the shell will be coming from the user
who is browsing the page and it's not going to be coming from the Web site.
So any code you write in JavaScript will be exploited or will run on the target user on the people who
see the pages.
And it's not on the web server.
So the web server is only going to be used as means of executing the code or delivering the code there
is three main types of accesses vulnerabilities persistent or stored reflected and done based
distort accesses gets stored into the database.
So the code that you inject will be stored into the database or into the page so that every time any
person views that page your code will be executed and the reflected one the code will only be executed
when the target user runs a specific you're well crafted or written by you.
So you'll be manipulating some sort of your l and send it to a target.
And when they run that target when they run that you are out the code will be executed the dawn based
results from javascript code written on the client.
So the code will actually be interpreted and run on the client side without having any communication
with the web server.
These could be very dangerous because sometimes web servers apply some sort of security infiltration
to check for excesses.
But with Dom based the code never gets sent to the web server.
So the code will be interpreted and run on the web browser without even interacting with the web server
and these will be present into web websites that update their content without refresh.
So we've all used Web sites where you put your user name for example and it loads in straight away without
having to check with the web server or you do you put some sort of a string.
And it does a search without communicating with the web server or does something without communicating
with web server.
So if you're able to inject into that then this injection will not be validated.
So it will be executed straightaway and bypass all validations.