N.J. Stat. Ann. § 2A:50-46

Whenever it is provided in a mortgage, or in the evidence of debt secured thereby, that the mortgagee may claim a default for the nonpayment of any municipal lien or liens on the mortgaged premises which shall have remained unpaid for a specified time, the holder of the mortgage, the municipal lien or liens not having been paid within the specified time, may pay or purchase the lien, taking an assignment thereof, and foreclose the mortgage only for the amount due for the municipal lien or liens.