Section 27. The officer authorized to serve the execution shall make the sale by public auction to the highest bidder, and convey by deed to the purchaser all the debtor's title to the land or rights so sold. Such deed shall, if the execution with the return thereon has been returned, be valid as against the debtor or any person claiming under him who has actual notice thereof and, if recorded within three months after such sale in the registry of deeds for the county or district where the land lies, shall be valid as against any other person.