A tightly contested final should have been settled by Firmino long before the 99th minute, but the usually reliable forward twice missed the target when well placed.
Liverpool also had a last-gasp penalty award struck off in normal time following a VAR review, giving Flamengo - victors over the Reds in the 1981 Intercontinental Cup final - a lifeline.
However, the Premier League leaders dominated the additional period, and Firmino finally found the net to tee up yet more celebrations on Merseyside.
