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All right, so welcome back, everyone.



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This is speech, and this is another very fresh section.



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This is about cross site scripting.



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Trust me, this is one of the most popular topic among the website application, security, vulnerability



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assessment or whatever you say, you know, ethical hacking for Web application as well.



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So Web site scripting has been there for as being there for a while.



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I mean, for many years, in fact.



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And it is very important to understand this.



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And but in order to understand the scripting, there are many documents.



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There are many articles for us.



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But we really if you really want to understand how this really works and what exactly this attack is



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all about, scripting is an attack.



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Remember this and this attack is only possible because of some vulnerability.



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OK.



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And we'll be working to understand what this vulnerability is all about.



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OK, and let's start from the beginning.



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Let's start from the fundamentals.



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Let's start from the web.



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Let's start from the JavaScript.



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That makes it possible.



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All right.



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So the that's why we have sort of a JavaScript, and it is very, very important to understand JavaScript



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because the now whatever you see on the Internet is all because of e-mail and JavaScript.



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OK, and for your information, Java and JavaScript is nowhere that although both our programming language,



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but they are both foir very much different.



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OK, I understand this what the purpose of JavaScript is to make the user experience more engaging,



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more useful.



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What happened, you know, you that even makes the job of developer pretty easier.



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Right.



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There are many forms that you fill up and you immediately get a problem saying, hey, you enter a wrong



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password.



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Hey, prior to entering the new password, it would have been seen.



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But this makes the when you make use of JavaScript as a coding language, it makes a very triggered



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or very spontaneous or very active response to the user saying, OK, I need to change it without in



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a very real time, without even filling up the entire form.



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You immediately get the response saying, OK, there's something wrong because you get a pop up on your



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windows saying, OK, change this, change that and understand.



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So that's all possible because of JavaScript, all lovely looking website or wonderful user interface



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on the you know, on their Web application.



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It's all possible because of JavaScript, whatever the file you see with its own JavaScript.



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Now, JavaScript has been available from the beginning, not from the user side, from the user side



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programming.



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When it's a user site, it's all all about Web browser.



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Right.



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So from the Web browser side of browser site programming, it has moved to the server side as well.



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And now because of no juice and bluejays express, is it made the job even more, you know, made the



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programming even more fantastic and makes the platform even more realistic and realtime.



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So that's why you see some heavy platform, you know, Web application.



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It's all possible because of JavaScript.



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Right.



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So it's a scrappy language will understand piece by piece.



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And when I say scripting language specifically, it's a it has a lot of dynamic content, a big multimedia



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and animated images.



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So it's all possible because of JavaScript.



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Then, as I told you, it's a client side language and it features there are many features of it storing



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the useful information like user credentials, not really credentials, but user related informations,



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you know, are forms, first name, last name, location, all the stuff there's JavaScript based form



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makes the job very easy.



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Pop up windows and all those type APIs.



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Of course, all the apps that you see, it's all based on API, I mean, Albie's and JavaScript and



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points.



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So that's where you get get and post APIs where you can share the information and you can fish the information



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with the EPA.



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Don't you see many of the travel website or maybe you log in to prove that?



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I'm sure there are many, many, you know, aggregator traveling website.



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You go there.



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But they don't really sell those stuff, right?



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They don't really.



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If you go to any hotel, dotcom or any any of those websites, they don't really sell those products



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by themselves rather than redirect you to somewhere else, but just give you the best product listed.



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That's all possible because of the EPA.



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So this all Web site, who could be aggregator, they fetches the information from thousands of website



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and make it available for you.



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And you look at Yahoo!



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Dot com.



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Right.



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So and Yahoo!



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You get the feed coming on the main page.



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You get the feed coming in from four news for, you know, for information related to weather forecast,



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for crooked news for any of the sports news, football matches, update and many others.



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So it's all possible because for every other feeds, website depends on the other dedicated website



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like Weather Channel.



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Right.



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So from there, get the feeds.



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That's all possible because of the API that the application programming interface and with data communicate



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to the other platform, other domains as Summerside use cases.



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Of course, I told you that make use of energy is expressed in single digits and many more.



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Right.



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So that's what makes the JavaScript so useful.



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Let's see how it does.



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It looks like when you you know, when you understand how how JavaScript makes the job pretty much interesting.



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So here is our system.



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Here is our time machine running, let's say a browser, maybe Chrome at this moment.



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So when I say about Web application, remember that the client is always Web browser.



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OK, it's not the end host.



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When I say the client side it.



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So the browser side.



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So all the intelligence of the Web browser sites on the browser itself.



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In fact, there's a JavaScript engine for every browser.



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So every browser have to have their JavaScript engine, which fetches the information from the server



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side and runs on the browser and give you the response rate.



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And on the Web server side, you have a website called Example Dot com.



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Right.



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The request goes to the server, the client in the request, because we SCDP get requests for maybe



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get requests could be on the you are right.



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For example, dot com.



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Maybe he just wanted to get the homepage.



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We want to reach out to example, dot com and want to browse it so it would be SCDP get request.



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Now what would be the response.



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The response could be two hundred.



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Okay.



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Right.



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That's a response quote if the site is available.



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Right.



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So the response would come back usually what is really the script is all about, because if you see



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JavaScript it is all embedded, it's all inserted into the e-mail code.



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What I mean to say is if your homepage has a JavaScript defined somewhere, it will simply be inserted



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into the e-mail code.



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And if you know the e-mail code, it has got two parts at the head and the body.



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So in the when the job you talk about JavaScript, you can have JavaScript defined anywhere.



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So if you let's say you inserted into the body, you just have to make sure you use the right syntax



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script starting with the and script and then just slash including actor.



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This is how the website really looks like.



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So maybe the website has nothing but just the website as a title.



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So it has to part it is it has got its esteemable header and the body is well and I'm talking about



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the body part in body.



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We have inserted this script and the script says, Alert, welcome, welcome.



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What, what's your name?



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And that's where the script get completed.



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Whatever you insert here, that becomes the program, that becomes the execution.



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So what are we trying to do is we are saying to this program, this code basically this is basically



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hosted on example dot com server.



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And this has this has got an e-mail page which says Pop alert is all about prompt or console or giving



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the prompt response output as on the browser.



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So whenever somebody open up the browser or reach out to the website, they get the prompt open on their



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browser, open on the browser, and it must say, welcome what to me for that the alert is the function



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which is being used in the back.



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And you see the same name.



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Right.



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And of course you need the code as well, which is.



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Missing here.



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So that's what you see if you zoom in, you get the idea on the browser, you see I have made it personally



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so you could see it says welcome what to name because we tried we made use of the script.



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OK, so that's how you get to see a prompt opening on your Chrome browser.



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And that is an embedded page.



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And this website says, welcome, what's your name?



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All right.



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So that's what the job of Java script.



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And that's what makes the Internet so scalable so faster as well, because that makes the the the response



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to the user pretty quick, very dynamic and pretty much on realtime.



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All right.



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So this is about the Java script and the next session will understand some of the security challenges



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with that and what that does to the next level of solving it.



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All right.



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So we'll see you then.