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Difference between revisions of "Testing for JavaScript Execution (OTG-CLIENT-002)"

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m (Andrew Muller moved page Testing for JavaScript Execution to Testing for JavaScript Execution (OTG-CLIENT-002): Align with Common Numbering)
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{{Template:OWASP Testing Guide v4}}
 
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== Brief Summary ==
+
== Summary ==
 
A JavaScript Injection vulnerability is a subtype of Cross Site Scripting (XSS) that involves the ability to inject arbitrary JavaScript code that is executed by the application inside the victim's browser. This vulnerability can have many consequences, like disclosure of a user's session cookies that could be used to impersonate the victim, or, more generally, it can allow the attacker to modify the page content seen by the victims or the application behavior.
 
A JavaScript Injection vulnerability is a subtype of Cross Site Scripting (XSS) that involves the ability to inject arbitrary JavaScript code that is executed by the application inside the victim's browser. This vulnerability can have many consequences, like disclosure of a user's session cookies that could be used to impersonate the victim, or, more generally, it can allow the attacker to modify the page content seen by the victims or the application behavior.
  
  
== Description of the Issue ==  
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== How to Test ==  
 
Such vulnerability occurs when the application lacks of a proper user supplied input and output validation. JavaScript is used to dynamically populate web pages, this injection occur during this content processing phase and consequently affect the victim.
 
Such vulnerability occurs when the application lacks of a proper user supplied input and output validation. JavaScript is used to dynamically populate web pages, this injection occur during this content processing phase and consequently affect the victim.
  
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== Black Box testing and example ==
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=== Black Box testing ===
 
Black box testing for  JavaScript Execution is not usually performed since access to the source code is always available as it needs to be sent to the client to be executed.<br>
 
Black box testing for  JavaScript Execution is not usually performed since access to the source code is always available as it needs to be sent to the client to be executed.<br>
  
  
== Gray Box testing and example ==
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=== Gray Box testing ===
 
'''Testing for JavaScript Execution vulnerabilities:'''
 
'''Testing for JavaScript Execution vulnerabilities:'''
  

Revision as of 07:28, 8 August 2014

This article is part of the new OWASP Testing Guide v4.
Back to the OWASP Testing Guide v4 ToC: https://www.owasp.org/index.php/OWASP_Testing_Guide_v4_Table_of_Contents Back to the OWASP Testing Guide Project: https://www.owasp.org/index.php/OWASP_Testing_Project

Summary

A JavaScript Injection vulnerability is a subtype of Cross Site Scripting (XSS) that involves the ability to inject arbitrary JavaScript code that is executed by the application inside the victim's browser. This vulnerability can have many consequences, like disclosure of a user's session cookies that could be used to impersonate the victim, or, more generally, it can allow the attacker to modify the page content seen by the victims or the application behavior.


How to Test

Such vulnerability occurs when the application lacks of a proper user supplied input and output validation. JavaScript is used to dynamically populate web pages, this injection occur during this content processing phase and consequently affect the victim.


When trying to exploit this kind of issues, consider that some characters are treated differently by different browsers. For reference see the DOM XSS Wiki.


The following script does not perform any validation of the variable rr that contains the user supplied input via the query string and additionally does not apply any form of encoding:

var rr = location.search.substring(1);
if(rr)
  window.location=decodeURIComponent(rr);
This implies that an attacker could inject JavaScript code simply by submitting the following query string: www.victim.com/?javascript:alert(1)


Black Box testing

Black box testing for JavaScript Execution is not usually performed since access to the source code is always available as it needs to be sent to the client to be executed.


Gray Box testing

Testing for JavaScript Execution vulnerabilities:

For example, looking at the following URL: http://www.domxss.com/domxss/01_Basics/04_eval.html


The page contains the following scripts:

<script>
function loadObj(){
 var cc=eval('('+aMess+')');
 document.getElementById('mess').textContent=cc.message;
}

if(window.location.hash.indexOf('message')==-1)
  var aMess="({\"message\":\"Hello User!\"})";
else
  var aMess=location.hash.substr(window.location.hash.indexOf('message=')+8);
</script>


The above code contains a source 'location.hash' that is controlled by the attacker that can inject directly in the 'message' value a JavaScript Code to take the control of the user browser.


References

OWASP Resources

Whitepapers