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.

We track 1 vulnerability of this type. 100% are rated high or critical, and the average CVSS score is 9.8.

How this weakness is prevented

• Architecture and Design: Specify in the design that any linked external document must not be granted access to the location object of the calling page.
• Implementation: 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: Do not use _blank targets. However, this can affect the usability of the application.