What is the ruling on someone who utters a strange word unrelated to Al-Fatiha while reciting it, then prostrates in forgetfulness after the Taslim?

Whoever speaks in prayer out of forgetfulness, his prayer is valid according to the preponderant opinion, and he is prescribed to perform the prostration of forgetfulness (sujud al-sahw). Therefore, what this person did when he uttered a word not from Al-Fatihah is correct, and his duty is discharged.