In Safari 10, Apple tightened up security so that plug-ins were not automatically enabled once installed. This can affect plug-ins like Adobe Flash and Microsoft Silverlight. When visiting a website that requires such a plug-in, you might get a message stating that the plug-in is not installed but this can vary.
For security reasons, it’s advisable to only activate specific web sites that need access to these plug-ins as they are an old technology riddled with security issues. To enable specific websites, please follow the instructions below.
1. Open Safari’s Preferences from the menu bar.
2. Select the Security category and then Plug-in Settings.
3. Select the plug-in on the left and then in the right pane choose On for the website where that particular plug-in needs activated.
4. Once that is finished click Done and close the Preferences window.