72 Pa. Stat. § 5883
Whenever, heretofore, any real property in the possession of the county commissioners of any county, which should have been turned over to the Tax Claim Bureau for sale in accordance with the provisions of the act known as the "Real Estate Tax Sale Law," approved the seventh day of July, one thousand nine hundred forty-seven (Pamphlet Laws, 1368), was instead sold at private or public sale by such county commissioners in accordance with what such county commissioners, in good faith, mistakenly believed the existing law of this Commonwealth to be, if the laws in effect as to such sales immediately prior to the effective date of the said "Real Estate Tax Sale Law" were fully complied with, all such commissioners' sales, public or private, and commissioners' deeds, are hereby ratified, confirmed, and validated, and the title to any such land purchased by any person at such commissioners' public or private sale, and the deed executed and acknowledged to such purchaser, are hereby declared to be as valid as if the entire transaction had been in full conformity with the said "Real Estate Tax Sale Law".
72 P.S. § 5883