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CAPEC-588: DOM-Based XSS

Attack Pattern ID: 588
Abstraction: Detailed
Status: Stable
Presentation Filter:
+ Description
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is inserted into the client-side HTML being parsed by a web browser. Content served by a vulnerable web application includes script code used to manipulate the Document Object Model (DOM). This script code either does not properly validate input, or does not perform proper output encoding, thus creating an opportunity for an adversary to inject a malicious script launch a XSS attack. A key distinction between other XSS attacks and DOM-based attacks is that in other XSS attacks, the malicious script runs when the vulnerable web page is initially loaded, while a DOM-based attack executes sometime after the page loads. Another distinction of DOM-based attacks is that in some cases, the malicious script is never sent to the vulnerable web server at all. An attack like this is guaranteed to bypass any server-side filtering attempts to protect users.
+ Likelihood Of Attack

High

+ Typical Severity

Very High

+ Relationships

The table(s) below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf, ParentOf, MemberOf 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.

+ Relevant to the view "Mechanisms of Attack" (CAPEC-1000)
NatureTypeIDName
ChildOfStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.63Cross-Site Scripting (XSS)
ParentOfDetailed 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.18XSS Targeting Non-Script Elements
ParentOfDetailed 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.32XSS Through HTTP Query Strings
ParentOfDetailed 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.86XSS Through HTTP Headers
ParentOfDetailed 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.198XSS Targeting Error Pages
ParentOfDetailed 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.199XSS Using Alternate Syntax
ParentOfDetailed 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.243XSS Targeting HTML Attributes
ParentOfDetailed 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.244XSS Targeting URI Placeholders
ParentOfDetailed 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.245XSS Using Doubled Characters
ParentOfDetailed 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.247XSS Using Invalid Characters
+ Prerequisites
An application that leverages a client-side web browser with scripting enabled.
An application that manipulates the DOM via client-side scripting.
An application that failS to adequately sanitize or encode untrusted input.
+ Skills Required
[Level: Medium]
Requires the ability to write scripts of some complexity and to inject it through user controlled fields in the system.
+ Resources Required
None: No specialized resources are required to execute this type of attack.
+ Consequences

The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality
Read Data
Confidentiality
Authorization
Access Control
Gain Privileges
Confidentiality
Integrity
Availability
Execute Unauthorized Commands
Integrity
Modify Data
+ Mitigations
Use browser technologies that do not allow client-side scripting.
Utilize proper character encoding for all output produced within client-site scripts manipulating the DOM.
Ensure that all user-supplied input is validated before use.
+ Example Instances

Consider a web application that enables or disables some of the fields of a form on the page via the use of a mode parameter provided on the query string.

http://my.site.com/aform.html?mode=full

The application’s client-side code may want to print this mode value to the screen to give the users an understanding of what mode they are in. In this example, JavaScript is used to pull the value from the URL and update the HTML by dynamically manipulating the DOM via a document.write() call.

<script>document.write("<p>Mode is: " + document.location.href.substring(document.location.href.indexOf('mode=') + 5) + "</p>");</script>

Notice how the value provided on the URL is used directly with no input validation performed and no output encoding in place. A maliciously crafted URL can thus be formed such that if a victim clicked on the URL, a malicious script would then be executed by the victim’s browser:

http://my.site.com/aform.html?mode=<script>alert('hi');</script>

In some DOM-based attacks, the malicious script never gets sent to the web server at all, thus bypassing any server-side protections that might be in place. Consider the previously used web application that displays the mode value. Since the HTML is being generated dynamically through DOM manipulations, a URL fragment (i.e., the part of a URL after the '#' character) can be used.

http://my.site.com/aform.html#mode=<script>alert('hi')</script>

In this variation of a DOM-based XSS attack, the malicious script will not be sent to the web server, but will instead be managed by the victim's browser and is still available to the client-side script code.

+ References
[REF-471] Amit Klein. "DOM Based Cross Site Scripting or XSS of the Third Kind". <http://www.webappsec.org/projects/articles/071105.shtml>.
[REF-472] Jakob Kallin and Irene Lobo Valbuena. "A comprehensive tutorial on cross-site scripting". <https://excess-xss.com/>.
+ Content History
Submissions
Submission DateSubmitterOrganization
2017-04-15CAPEC Content TeamThe MITRE Corporation
Modifications
Modification DateModifierOrganization
2017-08-04CAPEC Content TeamThe MITRE Corporation
Updated Resources_Required

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Page Last Updated or Reviewed: July 31, 2018