We are not specifically told who these people were nor how they became part of the church community. It is possible that they were some travelling Christian teachers or prophets as seen in Acts (Acts 11:27–30; Acts 21:10–11) and 2 John 1:10.1 These people would only have been welcomed if they claimed that they were followers of Jesus Christ.
4 For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.