Sorry, I'm having trouble understanding that acronym. What do you mean? In this case it was a TOFU error, as somebody was trying to SSH to a new AWS instance,

Sorry, I'm having trouble understanding that acronym. What do you mean? In this case it was a TOFU error, as somebody was trying to SSH to a new AWS instance, so they'd have trusted the certificate "on first use", even though they were actually SSHing into their network's router.