Our Win 8.1 and IE 11 does have enabled 3rd party Flash add-on feature called "Shockwave Flash Object". This is reference to Win8.1 and IE 11 attempting to view a Pano2vr FLASH output panorama and receiving a white screen with FLASH Err [click here to download flash] suggesting that we download Adobes flash plugin.
http://technet.microsoft.com/library/dn268945.aspx
Is Adobe Flash supported on Internet Explorer 11?
Adobe Flash is included as a platform feature and is available out of the box for Windows 8.1, running on both Internet Explorer and Internet Explorer for the desktop. Users can turn this feature on or off using the Manage Add-ons dialog box, while administrators can turn this feature on or off using the Group Policy setting, Turn off Adobe Flash in Internet Explorer and prevent applications from using Internet Explorer technology to instantiate Flash objects.
Important
The preinstalled version of Adobe Flash isn't supported on Internet Explorer 11 running on either Windows 7 SP1 or Windows Server 2008 R2 with SP1. However, you can still download and install the separate Adobe Flash plug-in.