NEW YORK – The black box around Xi Jinping’s corruption crackdown has long fuelled political gossip in China. Now, an underground market is emerging for selling purported secrets on who might be next to fall. Across China’s tightly controlled internet, the authorities are playing whack-a-mole to stop shadowy users who peddle access to groups claiming to leak details of which officials are under scrutiny, according to a recent report from Banyuetan, a magazine published by the official Xinhua News Agency. Members are typically charged a small entry fee, with access to more exclusive chat rooms promising better tips fetching as much as…