Since the last update of SSH Slaves plugin, the following warning is shown:

SSH Host Key Verifiers are not configured for all SSH slaves on this Jenkins instance. This could leave these slaves open to man-in-the-middle attacks. Update your slave configuration to resolve this.

I have three slaves, whose "Launch method" is "Launch agent via Java Web Start" for two of them and "Launch slave agents via SSH" for the third one.
Does the warning refer only to the last one?

The "Host Key Verification Strategy" I set is "Known hosts file Verification Strategy". What should I do to avoid that warning?