Links that invoke instances of Internet Explorer from within an Office product must be blocked in PowerPoint.
The Pop-up Blocker feature in Internet Explorer can be used to block most unwanted pop-up and pop-under windows from appearing. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). If the Pop-up Blocker is disabled, disruptive and potentially dangerous pop-up windows could load and present a security risk.
Set the policy value for Computer Configuration -> Administrative Templates -> Microsoft Office 2016 (Machine) -> Security Settings -> IE Security "Block popups" to "Enabled" and select 'powerpnt.exe'.