This is a problem I've been noticing since the youtube embed design change, at least from what I've noticed.
So what's happening is any web pages that have been added to homescreen that have a youtube video embedded will autoplay the first youtube video on screen in the youtube app. This doesn't happen when you open the same web page is opened in safari.
Basically any web pages that have a youtube video embedded are inaccessible due to it automatically redirecting you to the youtube app.
How can I stop this? Or is it something they've added that can't be fixed?
Update: found similar question with the proper workaround Embedded YouTube videos in HTML5 standalone app iOS 8.3 opening YouTube app
Unfortunately, the only workaround I've found so far is to disallow web application to runs in full-screen mode by removing:
<meta name="apple-mobile-web-app-capable" content="yes" />
Neither postponed iframe injection to dom, nor even putting iframe in iframe helps.
I really hope that it is not the intended behaviour and it will be resolved soon via iOS update; though until then I have to use server-side to detect OS 8_3 in useragent and deliver them modified version of webapp.