Unfortunately,
the local code of some existing Chrome apps (e.g., Lucidchart Diagrams)
sends postMessage with “*” as the destination, i.e., without
restricting the receiver’s origin. Malicious third-party Web code
running inside an iframe can “frame-bust” (i.e., navigate the main
frame of its WebView to the attacker’s URL), capture the message
and its contents, and change the main frame to its old URL.