Idézve a manból:
"There is a hard-coded list of one or more editors that visudo will use set at compile-time that may be overridden via the editor sudoers Default variable. This list defaults to vi. Normally, visudo does not honor the VISUAL or EDITOR environment variables unless they contain an editor in the aforementioned editors list. However, if visudo is configured with the --with-env-editor option or the env_editor Default variable is set in sudoers, visudo will use any the editor defines by VISUAL or EDITOR. Note that this can be a security hole since it allows the user to execute any program they wish simply by setting VISUAL or EDITOR."
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Hell is empty and all the devils are here.
-- Wm. Shakespeare, "The Tempest"