Najib Razak, the former Malaysian prime minister, who lost the parliamentary election to his former mentor, Mahathir Mohamad, after almost 10 years in office, was blacklisted from travelling overseas by the new authorities on Saturday. The move came immediately after Najib announced that he and his wife were taking a brief vacation abroad, starting Saturday. In a Facebook post, Najib, whose government was plagued by a massive financial scandal in the run-up to the election, wrote that he was planning to come back to the country next week. Mahathir, 92, became the oldest elected leader in the world when he was sworn in on Thursday.