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CAPEC-243: XSS Targeting HTML Attributes

Attack Pattern ID: 243
Abstraction: Detailed
Status: Draft
Presentation Filter:
+ Description
An adversary inserts commands to perform cross-site scripting (XSS) actions in HTML attributes. Many filters do not adequately sanitize attributes against the presence of potentially dangerous commands even if they adequately sanitize tags. For example, dangerous expressions could be inserted into a style attribute in an anchor tag, resulting in the execution of malicious code when the resulting page is rendered. If a victim is tricked into viewing the rendered page the attack proceeds like a normal XSS attack, possibly resulting in the loss of sensitive cookies or other malicious activities.
+ Typical Severity

Medium

+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
NatureTypeIDName
ChildOfDetailed Attack PatternDetailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.588DOM-Based XSS
ChildOfDetailed Attack PatternDetailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.591Reflected XSS
ChildOfDetailed Attack PatternDetailed Attack Pattern - A detailed level attack pattern in CAPEC provides a low level of detail, typically leveraging a specific technique and targeting a specific technology, and expresses a complete execution flow. Detailed attack patterns are more specific than meta attack patterns and standard attack patterns and often require a specific protection mechanism to mitigate actual attacks. A detailed level attack pattern often will leverage a number of different standard level attack patterns chained together to accomplish a goal.592Stored XSS
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
Explore
  1. Survey the application for user-controllable inputs: Using a browser or an automated tool, an adversary follows all public links and actions on a web site. They record all the links, the forms, the resources accessed and all other potential entry-points for the web application.

    Techniques
    Use a spidering tool to follow and record all links and analyze the web pages to find entry points. Make special note of any links that include parameters in the URL.
    Use a proxy tool to record all links visited during a manual traversal of the web application.
    Use a browser to manually explore the website and analyze how it is constructed. Many browsers' plugins are available to facilitate the analysis or automate the discovery.
Experiment
  1. Probe identified potential entry points for XSS targeting HTML attributes: The adversary uses the entry points gathered in the "Explore" phase as a target list and injects various malicious expressions as input, hoping to embed them as HTML attributes.

    Techniques
    Inject single and double quotes into URL parameters or other inputs to see if they are filtered out. Also use URL encoding to bypass filters.
    Use single or double quotes to close attribute evaluation and enter a new attribute that contains an expression.
  2. Craft malicious XSS URL: Once the adversary has determined which parameters are vulnerable to XSS, they will craft a malicious URL containing the XSS exploit. The adversary can have many goals, from stealing session IDs, cookies, credentials, and page content from the victim.

    Techniques
    Execute a script using an expression embedded in an HTML attribute, which avoids needing to inject a script tag.
    Send information gathered from the malicious script to a remote endpoint.
Exploit
  1. Get victim to click URL: In order for the attack to be successful, the victim needs to access the malicious URL.

    Techniques
    Send a phishing email to the victim containing the malicious URL. This can be hidden in a hyperlink as to not show the full URL, which might draw suspicion.
    Put the malicious URL on a public forum, where many victims might accidentally click the link.
+ Prerequisites
The target application must fail to adequately sanitize HTML attributes against the presence of dangerous commands.
+ Resources Required
The adversary must trick the victim into following a crafted link to a vulnerable server or view a web post where the dangerous commands are executed.
+ Mitigations
Design: Use libraries and templates that minimize unfiltered input.
Implementation: Normalize, filter and use an allowlist for all input including that which is not expected to have any scripting content.
Implementation: The victim should configure the browser to minimize active content from untrusted sources.
+ References
[REF-94] Jeremiah Grossman. "Attribute-Based Cross-Site Scripting". <http://jeremiahgrossman.blogspot.com/2007/07/attribute-based-cross-site-scripting.html>.
+ Content History
Submissions
Submission DateSubmitterOrganization
2014-06-23CAPEC Content TeamThe MITRE Corporation
Modifications
Modification DateModifierOrganization
2017-05-01CAPEC Content TeamThe MITRE Corporation
Updated Description Summary, Related_Attack_Patterns, Related_Weaknesses
2018-07-31CAPEC Content TeamThe MITRE Corporation
Updated Description Summary
2020-07-30CAPEC Content TeamThe MITRE Corporation
Updated Mitigations
2022-02-22CAPEC Content TeamThe MITRE Corporation
Updated Execution_Flow, Resources_Required
Previous Entry Names
Change DatePrevious Entry Name
2017-05-01Cross-Site Scripting in Attributes
2018-07-31XSS Targetting HTML Attributes
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Page Last Updated or Reviewed: October 21, 2021