If your lease does not address what would happen in the event of a Mortgage Forclosure you should consult an Attorney. My initial thoughts are that if you signed a Lease to rent the property, you are bound by the terms of the Lease as long as you continue to live in the house. In general it takes approximately a year in PA for the Mortgage Lender to take ownership, so depending on when your Landlord received notice from his/her Mortgage Company that forclosure proceedings were started - this will determine the amount of time you have left to start looking for another place to live before you are given notice to vacate the premises.
Good Luck and if you have any other questions regarding rental properties, feel free to contact me.
Cheryl J. McDonald
Short Sale Certified