If your company has a super tight security model, and the IT team needs to manually whitelist domains of your web-based tools, here are the ones that make Showcase work:

showcaseworkshop.com
*.showcaseworkshop.com
*.pndsn.com
fonts.googleapis.com
fonts.gstatic.com
www.gstatic.com
www.filestackapi.com
www.google-analytics.com