Cross-Site Scripting (XSS)

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Dangers of ‘XSS’ {
< Presenter: Hajiahmad Ahmadzada459>
Web Security
[Cross-Site Scripting]
}
hajiahmad.html Cross Site Scripting

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01 What is XSS?
02 How does XSS work?
03 What can XSS be used for?
Table Of ‘Contents’ {
}
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01 {
[What is cross-site
scripting (XSS)?]
}
Web Security
hajiahmad.html Cross Site Scripting

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Web Security
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02 {
[How does XSS work?]
}
Web Security
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XSS Proof of Concept; {
<script>alert(1)</script>
<p>
It's long been common practice to use the
alert() function for this purpose because it's
short, harmless, and pretty hard to miss when
it's successfully called.
}
</p>
Web Security
hajiahmad.html Cross Site Scripting

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Types of XSS attacks; {
where the vulnerability exists in client-side
code rather than server-side code.
where the malicious script comes from the
website's database.
Stored XSS
where the malicious script comes from the
current HTTP request.
Reflected XSS
DOM-based XSS
}
Web Security
hajiahmad.html Cross Site Scripting

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Reflected ‘XSS’ {
https://insecure-website.com/status?message=All+is+well.
<p>Status: All is well.</p>
Web Security
hajiahmad.html Cross Site Scripting
}
https://insecure-
website.com/status?message=<script>/*+Bad+stuff+here...+*/</
script>
<p>Status: <script>/* Bad stuff here... */</script></p>

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Stored ‘XSS’ {
<p>Hello, this is my message!</p>
Web Security
hajiahmad.html Cross Site Scripting
}
<p><script>/* Bad stuff here... */</script></p>

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DOM-based ‘XSS’ {
var search = document.getElementById('search').value;
var results = document.getElementById('results');
results.innerHTML = 'You searched for: ' + search;
Web Security
hajiahmad.html Cross Site Scripting
}
You searched for: <img src=1 onerror='/* Bad stuff here... */'>

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03 {
[What can XSS be used
for?]
}
Web Security
hajiahmad.html Cross Site Scripting

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What can XSS be used for?; {
An attacker who exploits a cross-site scripting vulnerability is
typically able to:
<p>
• 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.
</p>
}
Web Security
hajiahmad.html Cross Site Scripting

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How to prevent XSS attacks; {
Preventing cross-site scripting is trivial in some cases but can
be much harder depending on the complexity of the application and
the ways it handles user-controllable data.
<p>
• Filter input on arrival
• Encode data on output
• Use appropriate response headers
• Content Security Policy
</p>
}
Web Security
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CREDITS: This presentation template was
created by Slidesgo, including icons by
Flaticon, and infographics & images by
Freepik
Thanks; {
‘Do you have any questions?’
< Please keep this slide for attribution >
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}
Feel free to ask questions 🥰