Uh, not so fast.
Three highly regarded handwriting experts concluded the writing on the "Dear Mr. Hunt" note was Oswald's. The HSCA's fingerprint experts couldn't reach a firm conclusion on the note, but they noted several similarities between the writing on the note and Oswald's writing. Oswald's own wife, Marina, identified the handwriting as her husband's handwriting.
Yes, a few years ago a former Soviet KGB agent claimed the note was forged by the KGB to incriminate Howard Hunt, the ultra-conservative billionaire oil tycoon who made no secret of his hatred for JFK. This brings up an interesting point: If the handwriting for the "Dear Mr. Hunt" note could have been forged, then the handwriting on the envelope, order form, and money order that were used to buy the Mannlicher-Carcano rifle most certainly could have been forged as well.