Many website owners and advertisers have abused users by tab-under to show ads and redirect users to unwanted sites and chrome blocks it.
According to Bleeping computer, Google is working on blocking tab-under behavior in Chrome. Unsuspecting users scrolling or clicking on a page, website duplicates the current page in another tab and shows an ad or an alternate website in the page the user was initially reading.
Soon Chrome will block with an alert when tab-under ad or redirection detected in the browser.The proposals are to show an alert inside the page.
Google Engineers created a Demo site to show how tab under works.
This blocking feature will be arriving at chrome canary first, According to Chrome engineer Charles Harrison, the tab-under blocking feature will be supported on five of the six Blink platforms — Windows, Mac, Linux, Chrome OS, and Android, but not Android WebView.
Once the feature is ready, it will available in Chrome Canary under its own option on the chrome://flags settings page.