Not sure about the pageant part, but it's a major problem when connecting to a compromised server leaks the client's private key. (For example, if an attacker

Not sure about the pageant part, but it's a major problem when connecting to a compromised server leaks the client's private key. (For example, if an attacker has compromised server A and you connect to it, they can now use your key to connect to server B which you also use)