Disable Adobe Acrobat Plugin in Safari. There have been several security bugs in Adobe Acrobat in the past. Safari can view PDFs too.
The Acrobat/Reader 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 Acrobat/Reader plug-in will not work.
How to fix it
macOS 10.11 – 11.0
- Open “Safari” > “Preferences”
- 10.12-: Click the Websites button, then Internet Plug-ins: Website Settings.
- 10.11: Click “Security” > “Plugin-Settings…”
- Deselect “Acrobat Reader”
