This's the same as bug Bug 261443, but it's not yet fixed.
For e.g. if you try and drag a file over K3b which is at the taskbar, K3b's window won't get raised if the file has x bit set.
Reproducible: Didn't try
Any particular reason why?
And which version is this report about?
Ironic, this bug is not yet fixed.
I can confirm this bug in 4.9.1. The problem here is that shouldIgnoreDragEvent method of kde-workspace/plasma/desktop/applets/tasks/abstracttaskitem.cpp is set to ignore executable files, as executable files are "supposed" to be used as launchers.
One easy way to reproduce is by trying to drag and drop a file from an NTFS drive (without the noexec flag), since NTFS partition files are set to be executable by default.
Setting status to confirmed.
This is because dropping executables creates launchers. Dropping files, executables or otherwise, is a lower priority feature than launcher support, so when choosing what behaviour to adopt launcher support was selected.