I hate having to install VM-specific guest utils all the time when I just want to paste some text into the VM. Here's a script that emulates keyboard input and just works. ASCII-only, sadly.
Also, in VirtualBox, when you turn host-guest clipboard sync on in the VM settings (or set it to "Bidirectional"), it automatically syncs host clipboard contents to the VM clipboard, even if you never actually paste the clipboard contents into that VM. If you're running untrusted software in a VM and have guest utils installed, this might be a data leak vector you're not even aware of. So, install this script and only use guest-host clipboard sync if you really need it.
Also, in VirtualBox, when you turn host-guest clipboard sync on in the VM settings (or set it to "Bidirectional"), it automatically syncs host clipboard contents to the VM clipboard, even if you never actually paste the clipboard contents into that VM. If you're running untrusted software in a VM and have guest utils installed, this might be a data leak vector you're not even aware of. So, install this script and only use guest-host clipboard sync if you really need it.