What should the worshippers do if the Imam prayed three Rak'at in the Tarawih prayer and said the Taslim instead of two Rak'at, and they have not yet prayed Witr?

The Imam who prayed Dhuhr five rak'ahs must perform the two prostrations of forgetfulness (sujud (definition) al-sahw), and the congregants with him must also prostrate. This is based on the hadith (definition) of Ibn Mas'ud that the Prophet, peace and blessings be upon him, prayed Dhuhr five rak'ahs and then performed two prostrations after the taslim (definition). There is no difference in the prostration of forgetfulness between obligatory and supererogatory prayers according to the majority of scholars, due to the generality of the Prophet's saying, "If any of you forgets, let him prostrate two prostrations." And "If any of you forgets and adds or subtracts, let him prostrate two prostrations." So, if someone stands for a third rak'ah in the night prayer, similar to someone who stands for a third rak'ah in Fajr, Imam Malik held that he should complete it as four rak'ahs and then perform the prostrations of forgetfulness.