virtualbox – Error while installing Virtual box extension pack

I have downloaded Virtual box 7.0.6 (VirtualBox-7.0.6-155176-Linux_amd64.run) and its extension pack (Oracle_VM_VirtualBox_Extension_Pack-7.0.6.vbox-extpack) from Oracle’s site. Installation of the program was smooth. Not so for the extension. I tried to install it via GUI (File / Tools / Extension pack manager) and from terminal. In both cases it gives me the following error:

cd /opt/VirtualBox/
sudo VBoxManage extpack install ./Oracle_VM_VirtualBox_Extension_Pack-7.0.6.vbox-extpack
...
0%...NS_ERROR_FAILURE
VBoxManage: error: Failed to install "/opt/VirtualBox/Oracle_VM_VirtualBox_Extension_Pack-7.0.6.vbox-extpack"
VBoxManage: error: The installer failed with exit code 1: VBoxExtPackHelperApp: error: World writable: '/opt'
VBoxManage: error: Details: code NS_ERROR_FAILURE (0x80004005), component ExtPackManagerWrap, interface IExtPackManager
VBoxManage: error: Context: "RTEXITCODE handleExtPack(HandlerArg*)" at line 1912 of file VBoxManageMisc.cpp

The path /opt/VirtualBox/ is where the program was installed (I copied the extension pack overthere as well, just in case, after my attempts to install it from home failed with the same message).

My OS ist Lubuntu 20.04 64-bit. /opt/ has the permissions drwxrwxrwx and is owned by root. So is /opt/VirtualBox/.

P. S. Surely, I tried to install it without sudo. It makes no difference.

P. P. S. I had read many threads with description of the same problem (it is curious that majority of them are rather old) before I posted here. The set of advices effectively reduces to «Use ‘sudo’!».