Assalaam Alaikum Wa Rahmatullahi Wa Barakatuh,
1.The words of the Torah, the Bible, and the Psalms do not have the miraculousness of those of the Qur’an. They have also been translated again and again, and a great many alien words have become intermingled with them. Also, the words of commentators and their false interpretations have been confused with their verses. In addition, the distortions of the ignorant and the hostile have been incorporated into them. In these ways, the corruptions and alterations have multiplied in those Books. In fact, Shaykh Rahmat Allah al-Hindi, the well-known scholar, proved to Jewish and Christian scholars and priests thousands of corruptions in them, and silenced them. Nevertheless, despite these corruptions, in our times the celebrated Husayn Jisri RA extracted one hundred and ten indications to the prophethood of Muhammad (PBUH), and included them in his Risalat al-Hamidiya.
2.Also, many Jewish and Christian scholars acknowledged and admitted that the attributes of Muhammad the Arabian (Upon whom be blessings and peace) were written in their Books. The famous Roman Emperor Heraclius, who was a non-Muslim himself, said: “Jesus foretold Muhammad’s coming.”
Also, another Roman ruler called Muqawqis, the Governor of Egypt, and celebrated Jewish scholars and leaders such as Ibn Suriya, Zubayr b. Batiya, Ibn Akhtab and his brother Ka‘b b. Asad, although remaining non-Muslim, admitted: “He is described in our Books.”
Also, some of the well-known Jewish scholars and Christian priests gave up their obduracy on seeing Muhammad’s (PBUH) attributes as described in the above-mentioned books, and believed in him. They then pointed out these references to other Jewish and Christian scholars, and convinced them. Among them were the famous ‘Abd Allah b. Salam, Wahb b. Munabbih, Abu Yasir, the two sons of Sa‘ya, Asid and Tha‘laba, and Shamul.296 The latter lived at the time of Tubba‘, the ruler of Yemen. Shamul became a believer before Muhammad’s prophetic mission and without ever seeing him, just as Tubba‘ did. While the guest of the Bani Nadir before the prophetic mission, a gnostic called Ibn al-Hayyaban declared: “A prophet will soon appear, and this is the place to which he will emigrate.” He died there. Later, when that tribe was at war with God’s Messenger (Upon whom be blessings and peace), Asid and Tha‘laba came forward and cried out to the tribe: “By God, he is the one Ibn al-Hayyaban promised would come.” But they did not heed him, and paid the penalty.
Also, many of the Jewish scholars like, Ibn Yasin, Mikhayriq, and Ka‘b al-Ahbar, became believers on seeing the prophetic attributes in their Books, and silenced those who did not accept faith.
Therefore,it's possible that there have been more alterations after the age of Muhammed SAW.
http://www.lightofquran.info/q5.htm