Explanation
"Brute force attack in which stolen user account names and passwords are tested against multiple websites." CompTIA SY0-601 Official Study Guide Page 690 This is a poorly worded question and while credential stuffing is a type of brute force attack, the information given does not indicate multiple websites. At best, this looks like a password spraying attack, but it is more likely a brute-force attack. Also note the output reads
"unsername" and not "username" - perhaps irrelevant but the little things can and do matter