First: the Quran never says it’s confirming the Jewish and Christian canons that exist in the 7th century. It only claims to confirm what prior prophets actually taught including the gospel message Jesus actually taught. Jewish and Christian scriptural canons are not coextensive with what the prophets actually taught; they at best contain some extant prophetic teaching in meaning plus layers of post prophetic edits, redaction and interpretations. Second: the Jewish and Christian scriptures in their present form must be interpreted to arrive at Christian doctrines; they can also be interpreted in agreement with the Quran. So even if one grants the Quran confirming them, the dilemma argument requires the Quran to agree to Christian exegesis of the Bible - which the Quran definitely does not confirm and outright rejects.

@KhalilAndani It does more than once...sorry but you can't run from your own book.