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CWE-83: Improper Neutralization of Script in Attributes in a Web Page

 
Improper Neutralization of Script in Attributes in a Web Page
Weakness ID: 83 (Weakness Variant)Status: Draft
+ Description

Description Summary

The software does not neutralize or incorrectly neutralizes "javascript:" or other URIs from dangerous attributes within tags, such as onmouseover, onload, onerror, or style.
+ Time of Introduction
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Confidentiality
Integrity
Availability

Technical Impact: Read application data; Execute unauthorized code or commands

+ Observed Examples
ReferenceDescription
Bypass filtering of SCRIPT tags using onload in BODY, href in A, BUTTON, INPUT, and others.
guestbook XSS in STYLE or IMG SRC attributes.
Javascript in onerror attribute of IMG tag.
XSS in web-based email product via onmouseover event.
XSS via script in <P> tag.
Onload, onmouseover, and other events in an e-mail attachment.
Onmouseover and onload events in img, link, and mail tags.
Javascript in onmouseover attribute in e-mail address or URL.
+ Potential Mitigations

Phase: Implementation

Carefully check each input parameter against a rigorous positive specification (white list) defining the specific characters and format allowed. All input should be neutralized, not just parameters that the user is supposed to specify, but all data in the request, including tag attributes, hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. We often encounter data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.

Phase: Implementation

Strategy: Output Encoding

Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.

The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.

Phase: Implementation

With Struts, write all data from form beans with the bean's filter attribute set to true.

Phase: Implementation

Strategy: Identify and Reduce Attack Surface

To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XMLHTTPRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.

Effectiveness: Defense in Depth

+ Weakness Ordinalities
OrdinalityDescription
Primary
(where the weakness exists independent of other weaknesses)
+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory990SFP Secondary Cluster: Tainted Input to Command
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness VariantWeakness Variant82Improper Neutralization of Script in Attributes of IMG Tags in a Web Page
Development Concepts (primary)699
Research Concepts (primary)1000
+ Causal Nature

Explicit

+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERXSS using Script in Attributes
Software Fault PatternsSFP24Tainted input to command
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Observed_Example, Taxonomy_Mappings, Weakness_Ordinalities
2009-10-29CWE Content TeamMITREInternal
updated Relationships
2010-04-05CWE Content TeamMITREInternal
updated Description, Name, Related_Attack_Patterns
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-03-29CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11XSS using Script in Attributes
2010-04-05Failure to Sanitize Script in Attributes in a Web Page
Page Last Updated: July 30, 2014