In added time for the championship team substitute Josh Coburn scored the 1-0 winner and sent the home fans cheering,
And the 19-year-old told bbc sport "I have nothing to say! In front of the Riverside Stadium, it doesn't get any better than that against a Premier League team."
"I hit it as hard as I could and luckily it went in. It was amazing. I can't put it into words.
"All the players are excited. The fans support the players too. Hopefully we can carry on and get another big team in the next round."
The 19-year-old, who joined three years ago after being released by Sunderland, has been praised by his former defender and Boro manager.
Tottenham stunned to see Middlesbrough
Watch all the latest FA Cup highlights and reactions here. This is Middlesbrough's second successive Premier League scalp, having beaten Manchester United on penalties at Old Trafford to reach this stage.
"The fans give us the energy to put in the best performance," said boss Chris Wilder.
"We are happy to be in the next round, I would be happy if it was a home game. A great gift to everyone who has joined this club.
“We want to make memories. We have one at Old Trafford and I'm sure we have one in our own stadium, which is brilliant."
Manchester and Tottenham have also been knocked out by Middlesbrough from the FA cup
By beating Manchester United, Middlesbrough has confidence and optimism.