COMMON WEAKNESS ENUMERATIONIncomplete

CWE-1022

Use of Web Link to Untrusted Target with window.opener Access

The web application produces links to untrusted external sites outside of its sphere of control, but it does not properly prevent the external site from modifying security-critical properties of the window.opener object, such as the location property.

Abstraction

Variant

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The web application produces links to untrusted external sites outside of its sphere of control, but it does not properly prevent the external site from modifying security-critical properties of the window.opener object, such as the location property.

Extended description

When a user clicks a link to an external site ("target"), the target="_blank" attribute causes the target site's contents to be opened in a new window or tab, which runs in the same process as the original page. The window.opener object records information about the original page that offered the link. If an attacker can run script on the target page, then they could read or modify certain properties of the window.opener object, including the location property - even if the original and target site are not the same origin. An attacker can modify the location property to automatically redirect the user to a malicious site, e.g. as part of a phishing attack. Since this redirect happens in the original window/tab - which is not necessarily visible, since the browser is focusing the display on the new target page - the user might not notice any suspicious redirection.

Terminology

Alternate terms and usages

tabnabbing

Root cause

How and when does the problem arise?

Lifecycle phase

Architecture and Design

This weakness is introduced during the design of an application when the architect does not specify that a linked external document should not be able to alter the location of the calling page.

Lifecycle phase

Implementation

This weakness is introduced during the coding of an application when the developer does not include the noopener and/or noreferrer value for the rel attribute.

Risk

What does successful exploitation lead to?

Alter Execution Logic

Affected security scopes: Confidentiality

The user may be redirected to an untrusted page that contains undesired content or malicious script code.

Defence

How is it prevented and fixed?

Architecture and Design

Architecture and design approach

Detail
Specify in the design that any linked external document must not be granted access to the location object of the calling page.

Implementation

Implementation-phase defence

Detail
When creating a link to an external document using the <a> tag with a defined target, for example "_blank" or a named frame, provide the rel attribute with a value "noopener noreferrer". If opening the external document in a new window via javascript, then reset the opener by setting it equal to null.

Implementation

Implementation-phase defence

Detail
Do not use "_blank" targets. However, this can affect the usability of the application.

Verification

How is it detected?

Automated Static Analysis

High
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)