The scoreline doesn’t really do the Gunners justice as they largely dominated proceedings in the Premier League, with Bukayo Saka scoring the only goal of the game in the first half.
They are now in fourth on 54 points, four points clear of Man Utd in fifth.
Arsenal also hold a game in hand over the Red Devils.
Most of the teams in the Premier League have had a free weekend due to FA Cup fixtures.
On Friday, Leeds won in similarly dramatic circumstances, with Luke Ayling scoring in injury time as the Yorkshire outfit won 3-2 at Wolves.
Leicester v Brentford
View our detailed player statistics for the Premier League at the link below.