The latest claim came as a female pupil, who alleged she was raped by a teacher in 1990 while attending its former junior school, spoke to the BBC.
Kate, who we are not identifying, told her story to the police two years ago but the case collapsed.
Gordonstoun said it was committed to assisting the police.
BBC Scotland spoke to Kate, who claimed she was raped by a teacher while on a camping trip in 1990 when she was a 12-year-old pupil at Gordonstoun's prep School, Aberlour House.
She eventually told her story to the police but the case collapsed after another witness withdrew her statement at the last minute.
Kate, who now lives in England, has now joined a group of former pupils who are pressing for a change in Scotland's corroboration laws and asking the school to deal with the many claims of bullying and abuse.
She said: "I do remember feeling very isolated, because it was the first night of the trip it happened. I just had no idea what had just happened to me.
"I hold the school in great esteem but obviously there were failings at the time.
"An apology is always a nice thing to hear. I know it's a different era but it would be nice to hear an apology."
Police Scotland confirmed that it has been contacted by another former pupil in recent days concerning what it calls a historical matter at Gordonstoun.
In a statement, Gordonstoun said: "We were shocked and saddened to hear of Kate's account of her experience at Aberlour House.
"Cases of this kind must be unimaginably distressing for the victims and we are committed to managing any case of historic abuse as openly as possible, assisting the police with any inquiry and, above all, supporting victims in any way we can.
"We have given the investigating police unrestricted access to the archive records we hold for Aberlour House.
"We were surprised and disappointed that her case did not go to court and remain available to assist future investigations."
Another former pupil of Gordonstoun public school in Moray has contacted police over claims of historical sexual abuse, it has emerged.