'American Idol' Finalist -- Busted In Undercover Drug Sting (MUG SHOT)

"American Idol" finalist Curtis "C.J." Harris was arrested in an undercover drug bust for allegedly selling oxycodone and marijuana.

Law enforcement officials in Alabama tell us Harris was arrested Thursday after allegedly selling drugs to a confidential informant.

Harris was hit with 3 counts of felony distribution of a controlled substance. We're told he's still in custody and is being held on a $90k bond.

Harris finished 6th during season 13 of the show ... Caleb Johnson took home the crown that year.