This paper documents a minor but somewhat easy way to compromise air gapped systems that share a kvm.
You can download it from the following link: https://packetstormsecurity.com/files/download/147445/KVM-airgap.pdf
Source: https://packetstormsecurity.com/files/147445/Bridging-The-Gap-Between-SIPR-And-NIPR-Using-KVM-Switches.html