download appimage from here https://github.com/oguzhaninan/Buka/releases create a data project in k3b and add the just downloaded file k3b shows this message "The file you are about to add to the project is an ISO 9660 image. As such it can be burned to a medium directly since it already contains a file system. Are you sure you want to add this file to the project?" K3b 17.08.3 on Arch Linux
Nice test! it is smart to DIFF AppImage and ISO :)
K3B 17.12.1 is affected.
Reproducible with k3b 18.04.2 on Arch Linux.
This is because a type-1 AppImage is also a valid ISO 9660 file: https://github.com/AppImage/AppImageSpec/blob/master/draft.md#type-1-image-format