In PowerPoint you can created a "HotSpot" which is a graphic image or picture file that can be linked to an external URL. These HotSpots are supported, however you will need to have your external link begin with HTTPS. External links in HotSpots that begin with HTTP are unsupported at this time and could lead to Error thumbnails in the "Manage Slides" section of the presentation edit menu.
Please note that HotSpots with internal links (e.g. links to bring you to other slides within the PowerPoint deck) are not supported at this time. All HotSpots will need to be linked to external websites. You can link to other slides within a Brainshark Presentation by using the "Branching" option from a Question Slide.