WIY,
No one knows who wrote it. Some people think it was written during the times of the Rishonim, some people think it was written in the times of the Gaonim. Rashi never cites it which is some evidence that it either didn’t exist, was obscure, or Rashi didn’t hold of it. Sof Davar: be wary of quoting any information from it unless you have an additional source.