RCW 11.56.115: Effect of confirmation.

No petition or allegation thereof for the sale of real estate shall be considered jurisdictional, and confirmation by the court of any sale shall be absolutely conclusive as to the regularity of all proceedings leading up to and including such sale, and no instrument of conveyance of real estate made after confirmation of sale by the court shall be open to attack upon any grounds whatsoever except for fraud, and the confirmation by the court of any such sale shall be conclusive proof that all statutory provisions and all orders of the court with reference to such sale have been complied with.