Maupay scored the decisive goal in the 2-1 victory, Albion's first over a big-six club over the past two-and-a-half seasons.
Dunk said: "It's a great night for us. We made it tough for ourselves after the way we played in the first half when we were excellent and probably should have been further than one goal ahead.
"We expected a reaction and Arsenal showed what sort of side they could be at the start of the second half. We showed great character to hit back and get the win.
Goalscorer Maupay added: "We played well at Liverpool and did so again tonight but the difference was we got the win.
"It will give us a lot of confidence for Sunday's game against Wolves."