A top Yahoo official who has come under fire for the company's role in the 2004 imprisonment of a dissident in China apologised on Thursday for failing to tell US lawmakers that Yahoo knew more about the case than he initially acknowledged in testimony last year...The apology marks a shift in strategy at Yahoo, to strike a more conciliatory tone...Yahoo could still be vulnerable to future human rights-related cases involving Yahoo China, since Alibaba's boss, Jack Ma, made no secret of his willingness to co-operate closely with Beijing's authorities and with any investigations into users.