First let me start with a simple definition of the word cult. A cult in the religious sense is any group that claims to be christian, uses Christian terminology, but deviates in its basic theology from the Historic Christian faith. This deviation usually centers around the person and work of Jesus Christ. This usually includes the authority fo the Bible, the doctrines of God, the Holy Spirit, mankind, and salvation. Since most cults appeal to the Bible as the source for most of it's teachings, cults misuse the Bible in a number of ways.
Some cults suppliment the Bible with another authority or revelation.
A good example of this is the Mormons. Another way that cults misuse the Bible is through misquoting scriptures and passages. Cults often have to come up with their own translation of the Bible in order to support their abhorant theology. This has obviously been changed to support their belief that Jesus Christ is the Son of God, but not God the Son. The answer is that they are not saved and do not have the Holy Spirit dwelling within them.