My landlord is 18 months into foreclosure and she holds my security deposit. What are my rights in New Jersey and how do I regain my deposit?

First to regain your security deposit you have to move. The landlord is under no compulsion to return the deposit as long as you remain a tenant. Within 30 days of your vacating the property the landlord must return the deposit or a written account of how it was used. For more info on deposits see New Jersey Security Deposit Limits and Deadlines | Nolo.com

As noted on that site, the landlord is supposed to place the deposit in an interest bearing account and pay you the interest. However, he may be exempt from that depending on the type of unit.

Until the foreclosure is finalized, he still owns the property and can still come out of foreclosure. So its up to you whether you want to move. In case of foreclosure the new owners must give you 90 days to vacate, though that law expires at the end of the year. If you have a lease, they have to honor that lease. At the least they have to give you 30 days notice to vacate.