When I installed VirtualBox 5.1 by instructions on Download page, everything finished successful.
When I tried run VirtualBox the error was showed:
VirtualBox: supR3HardenedMainGetTrustedMain: dlopen("/usr/lib/virtualbox/VirtualBox.so",) failed: libQt5X11Extras.so.5: cannot open shared object file: No such file or directory
This can be fixed by install X11 extras:
dnf install qt5-qtx11extras.x86_64
After installation the library the error was shoved:
Qt FATAL: This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, xcb.
Reinstalling the application may fix this problem.
Aborted (core dumped)
This can be fixed by install X11 xkb common:
dnf install libxkbcommon-x11.x86_64
After those fixes everything works fine.
I repored it to Oracle here