Md. Code, Tax - Property § 14–823

The certificate of sale or assignment of the certificate of sale is presumptive evidence in all courts in all proceedings by and against the purchaser, and the purchaser’s representatives, heirs and assigns, of the truth of the statements in the certificate of sale or assignment of the certificate of sale, of the title of the purchaser to the property described in the certificate of sale or assignment of the certificate of sale, and of the regularity and validity of all proceedings had in reference to the taxes for the nonpayment of which the property was sold and the sale of the property.