Home > CAPEC List > CAPEC-591: Reflected XSS (Version 3.0)  

CAPEC-591: Reflected XSS

Attack Pattern ID: 591
Abstraction: Detailed
Status: Stable
Presentation Filter:
+ Description
This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is “reflected” off a vulnerable web application and then executed by a victim's browser. The process starts with an adversary delivering a malicious script to a victim and convincing the victim to send the script to the vulnerable web application. The most common method of this is through a phishing email where the adversary embeds the malicious script with a URL that the victim then clicks on. In processing the subsequent request, the vulnerable web application incorrectly considers the malicious script as valid input and uses it to creates a reposnse that is then sent back to the victim. To launch a successful Reflected XSS attack, an adversary looks for places where user-input is used directly in the generation of a response. This often involves elements that are not expected to host scripts such as image tags (<img>), or the addition of event attibutes such as onload and onmouseover. These elements are often not subject to the same input validation, output encoding, and other content filtering and checking routines.
+ 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 fail to adequately sanitize or encode untrusted input.
+ Skills Required
[Level: Medium]
Requires the ability to write malicious scripts and embed them into HTTP requests.
+ 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 strict type, character, and encoding enforcement.
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 server-side code may want to display this mode value in the HTML page being created to give the users an understanding of what mode they are in. In this example, PHP is used to pull the value from the URL and generate the desired HTML.

<?php echo 'Mode is: ' . $_GET["mode"]; ?>

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>

Reflected XSS attacks can take advantage of HTTP headers to compromise a victim. For example, assume a vulnerable web application called ‘mysite’ dynamically generates a link using an HTTP header such as HTTP_REFERER. Code somewhere in the application could look like:

<?php echo "<a href=”$_SERVER[‘HTTP_REFERER’]”>Test URL</a>" ?>

The HTTP_REFERER header is populated with the URI that linked to the currently executing page. A web site can be created and hosted by an adversary that takes advantage of this by adding a reference to the vulnerable web application. By tricking a victim into clicking a link that executes the attacker’s web page, such as:

"http://attackerswebsite.com?<script>malicious content</script>"

The vulnerable web application (‘mysite’) is now called via the attacker’s web site, initiated by the victim’s web browser. The HTTP_REFERER header will contain a malicious script, which is embedded into the page by the vulnerable application and served to the victim. The victim’s web browser then executes the injected script, thus compromising the victim’s machine.

+ References
[REF-476] Watchfire Research. "XSS vulnerabilities in Google.com". Full Disclosure mailing list archives. <http://seclists.org/fulldisclosure/2005/Dec/1107>.
+ 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

More information is available — Please select a different filter.
Page Last Updated or Reviewed: July 31, 2018