Non-authentic parts of Bhavishya Purana

In a nutshell, tampering with the Bhavisya P. is connected to the
anti-Vedic agenda of several Muslim and Western groups in recent
past during the British rule in India. We don't have a copy predating
British rule in India.

Religion historian and theologian Bhakti Ananda Goswami writes
(some of his writings are online, esp. on www.saragrahi.org):

The "Bhavishya Purana" is another Vaishnava shastra that has
definitely been redacted for a Muslim-related socio-political effect.
The passages in the Bhavishya Purana regarding Mohammed and Jesus, and
more modern figures, have no history in any verifiably ancient
editions, and are written in a form containing clear connections to
Ishmaelite Shia Muslim and late Biblical traditions. These insertions
in the text are obvious to properly trained linguistic scholars, and
those who have some understanding of the history of the text, but the
devotees are accepting this late fraudulent edition of their sacred
literature as authentic!

Concerning the redacted Bhavisya Purana and the inserted portions
of its modern published text, description of the seven mlecchacaryas
Adam, Enoch, Noah, Moses, Buddha, Jesus and Muhammad parallels Shia or
Ishma'ili heirohistory (p. 278). To understand the inauthenticity of
these inserted portions of text, it is enough to note that throughout,
the Biblical story references use sanskritized Islamic Arabic names.
Thus the names and stories have clearly come into the Purana not from
any sui generis transcendent or even earliest Biblical Hebrew, Greek
or Eastern-rite language Catholic source, but from a much later Arabic
/ Muslim source. As with the "Book of Mormon", the language used to
convey the story is a complete give-away to its true human origin. In
the case of Smith's "Book of Mormon", its King James Bible version
references are clear. In the case the late additions to the
Bhavisya Purana, their Muslim Arabic and British influences are
clear. One does not have to consider the issues of when the insertions
were made, or what the motive was, to recognize that these passages
have been added from some Muslim, Arabic or British-influenced source.
The British frame-of-reference and sanskritized Arabic language itself
reveals the fact throughout. In addition, Muslim traditions (from the
Hadith, etc.) and usages appear the insertions (p. 277) and such
sanskritized Muslim names, as found in the text are well attested in
19th century Bengali (p. 277).

Many scholars have studied these additions to the text. The issue
is not whether there can be prophetic scriptures, but whether these
specific passages are authentic parts of the original sanskrit text,
or if they have been added. Any honest analysis of the language of the
additions clearly shows that they are from a different source than the
rest of the text. If a person does not know that these were added,
they cannot be faulted fro citing them as part of an authentic Purana.

In the additions to the Pratisarga Parva of the Bhavisya Purana,
which is not a Vaishnava sattvic Purana, but is rather classed as
a tamasic Shakta Purana (p. 220), all the Biblical references appear
to be sanskritized Arabic (p. 276, 277) and the general presentation
shows Shia and even Ahmaddiya Muslim influences.

Here is the most respected current work that addresses the research
which has been done on the additions to the Maha Bhavisya Purana.
The page numbers given above are from this text.

Draupadi Among Rajputs, Muslims and Dalits: Rethinking India's Oral
and Classical Epics. Alf Hiltebeitel. Delhi, Oxford University Press,
2001, xiv, 560 p., ISBN 019-5655044

Hiltebeitel's book gives much needed background on the role of the
Muslim messianic groups in the reshaping of Rajput and Dalit oral
traditions. It includes some important specifics on the redaction of
the Bhavishya Purana, and shows how many Rajput and Muslim traditions
were amalgamated. I think this book is a top priority resource for
understanding one important aspect of the genesis of all the present
problems in which an element of Muslim messianism is active. Since it
deals with the early Nizari roots of the phenomenon in the North West
India-Afghan region, it is invaluable.