CWE-1021 Improper Restriction of Rendered UI Layers or Frames

The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain.

• Access Control: Gain Privileges or Assume Identity, Bypass Protection Mechanism, Read Application Data, Modify Application Data — An attacker can trick a user into performing actions that are masked and hidden from the user's view. The impact varies widely, depending on the functionality of the underlying application. For example, in a social media application, clickjacking could be used to trick the user into changing privacy settings.

• [Implementation] Use the "frame-ancestors" directive in the Content Security Policy, which is intended to define restrictions when it comes to allowing embedded content [REF-1544]. • [Implementation] The use of X-Frame-Options (now partially obsolete as of September 2026 [REF-1545]) allows developers of web content to restrict the usage of their application within the form of overlays, frames, or iFrames. The developer can indicate from which domains can frame the content. The concept of X-Frame-Options is well documented, but implementation of this protection mechanism is in development to cover gaps; often, there is a need for allowing frames from multiple domains. • [Implementation] Use a "frame-breaker" script in each page that should not be framed. This is very helpful for legacy browsers that do not support the X-Frame-Options security feature previously mentioned (which is now partially obsolete). • [Implementation] In addition to frames or iframes as previously mentioned, the web application is expected to place restrictions on whether it is allowed to be rendered within objects, embed, or applet elements.

• Automated Static Analysis: 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.)

• CVE-2017-7440: E-mail preview feature in a desktop application allows clickjacking attacks via a crafted e-mail message • CVE-2017-5697: Hardware/firmware product has insufficient clickjacking protection in its web user interface • CVE-2017-4015: Clickjacking in data-loss prevention product via HTTP response header. • CVE-2016-2496: Tapjacking in permission dialog for mobile OS allows access of private storage using a partially-overlapping window. • CVE-2015-1241: Tapjacking in web browser related to page navigation and touch/gesture events. • CVE-2017-0492: System UI in mobile OS allows a malicious application to create a UI overlay of the entire screen to gain privileges.