Available in Chrome 46+ | View on GitHub | Browse Samples
From now on, sandboxed frames will block modal dialogs by default to
prevent them from popping up confusing, modal messages to users. This includes the infamous
window.alert(), window.confirm(),
window.print() and window.prompt().
However if you really (really) want to allow modal dialogs inside a sandboxed
frame, you can still add "allow-modals" to its
"sandbox" attribute.
<!-- No sandbox there... Modal dialogs will pop up -->
<iframe id="red" src="iframe.html"></iframe>
<!-- Sandbox frame will execute javascript but block modal dialogs -->
<iframe id="green" src="iframe.html" sandbox="allow-scripts"></iframe>
<!-- Sandbox frame will execute javascript and show modal dialogs -->
<iframe id="blue" src="iframe.html"
sandbox="allow-scripts allow-modals"></iframe>