Rivka Nir argues in The First Christian Believer that the John the Baptist passage in Josephus's Antiquities is an interpolation.

Vridar blog posts setting out her case:

1. John the Baptist: Another Case for Forgery in Josephus

2. Early Thoughts on Authenticity of the John the Baptist Passage in Josephus

3. John the Baptist's Place in Josephus's Antiquities

4. On John the Baptist per Josephus - and the murder of Zechariah son of Jehoiada

5. What Did Josephus Think of John the Baptist?

6. John the Baptist in Josephus - What was his baptism?

7. John the Baptist - Another Case for Forgery in Josephus (conclusion)