He is the source of your life in Christ Jesus, whom God made our wisdom, our righteousness and sanctification and redemption; therefore, as it is written, “Let him who boasts, boast of the Lord.” [1 Corinthians 1:30–31]
Protestants do not say that God merely imputes wisdom, redemption, or sanctification to us but that He gives us these things actually. Therefore He also gives us justification (“righteousness” above) actually and not merely by imputation.
Aquinas, Etc. 
I’ve heard Protestants address this verse by saying that Jesus gives us these things differently, and thus imputation is by no meas ruled out. They argue that this is especially true because Paul distinguishes between righteousness and sanctification here, and that redemption is not ‘infused’.
I think it’s safer to argue that righteousness here refers to ‘faithfulness’ to the salvation promises, especially as found in Jeremiah 33:14-16.