Next Steps for Legacy Safari Plug-ins
By default, Safari [10] no longer tells websites that common plug-ins are installed. It does this by not including information about Flash, Java, Silverlight, and QuickTime in
navigator.pluginsandnavigator.mimeTypes. This convinces websites with both plug-in and HTML5-based media implementations to use their HTML5 implementation.[…]
When a website directly embeds a visible plug-in object, Safari instead presents a placeholder element with a “Click to use” button. When that’s clicked, Safari offers the user the options of activating the plug-in just one time or every time the user visits that website. Here too, the default option is to activate the plug-in only once.
