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Let's quickly talk about preventing cross site scripting.

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So how might we prevent cross-eyed scripting.

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Well there's a few different ways and this isn't even everything.

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Well let's talk about this.

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So first we have encoding now encoding is converting a control character to its escape sequence.

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OK.

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So for example here you see that we have the less than symbol becomes the ampersand L T and then a semicolon.

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So if we had script then script would just become Ampersand LTE semicolons script etc. you see the example.

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OK.

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So we're doing that.

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So that these symbols are not interpreted for like example an Excel tag or in this situation the script

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itself.

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You just can't interpret it.

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We can't use that character anymore.

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Right.

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And that's a very common way of doing things.

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Another thing is filtering so where you just take script and you strip out everything and anything and

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then just becomes script.

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So any of those characters that you don't want in there they just get wiped out basically.

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Right.

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So we say hey we don't want that.

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We're going to take it out.

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Another one is validating.

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So that's comparing inputting it's like a white list or a set of known good numbers.

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Say for example you have an account number and you type in the account number well if the account number

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is not in a set of known good numbers then it's not going to validate and it's going to prevent that

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from even reaching server side right or reaching an attack level.

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And then lastly there's sanitization which is basically a combination of everything and that's really

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what you're after is this combination of encoding filtering validating and making sure that this malicious

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activity and malicious code cannot be injected into your Web site so special note goes out to the H

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TTP only flag.

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So if you've been paying attention and birth sweet and looking at your cookies when your cookies get

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set a cookie can have an HP only flag and a secure flag.

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We're curious more for cross site scripting about the TTP only flag because its purpose is to prevent

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cookies from actually being observed by unauthorized parties.

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OK.

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So what that means is if we do a javascript and we try to steal cookie via javascript if we have the

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HP only flag we're not going to be able to see that cookie.

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We'll steal that cookie.

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So that will also help prevent this.

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So there's a bunch of different things that we can do and help guide this long.

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There's also headers out there that are a cross site scripting best practice headers that we can utilize

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to help prevent this as well.

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A lot of modern browsers are starting to help out here and prevent these.

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So this is a very very common exploit that you see and I would say out of all the things I have found

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the most bugs on it's probably cross site scripting level would be up there on the number one for me.

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So you'll see this all the time.

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So that is it for cross-eyed scripting.

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Hopefully you learned a bit here and you know you just take away the big takeaways are what it does

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why it's malicious and the three types of cross-eyed scripting which are reflected stored and done based.

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So from here we're going to talk a high level of insecure D serialization in the next video which is

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number eight on our list.

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We've only got three more to go so I will see over in the next video.