Christina Aguilera caused a stir among her fans after sharing a series of sizzling photos – including one of her topless.The Fighter singer posed for a number of Polaroid snaps to highlight her new Pride clothing collection, which she announced in May.MORE: Christina Aguilera plunges into pool in backless swimsuit – and she looks incredibleOne eye-catching photo features Christina wearing a pair of $25 black briefs with neon lips emblazoned on the front and her nickname, 'Xtina', written across