Adobe Flash has caused many problems in the past, with critical vulnerabilities frequently being exposed and Adobe regularly being required to release security updates.
The Flash plug-in for Apple Safari is based on Netscape Plug-In API (NPAPI), which is supported only till Safari version 11. In Safari 12, support for NPAPI plug-ins is removed, and hence the current Flash plug-in will not work.
How to fix it
macOS 10.11 – 11.0
- Select Safari and click Preferences.
- 10.12-: Click the Websites button, then Internet Plug-ins: Website Settings.
- 10.11: Click “Security” > “Plugin-Settings…”
- Deselect Adobe Flash Player.
