Owner signed lease one month before auction

[Tara G.]

We bid on a SFH atthe courthouse and are the highest bidders after the ten day upset period. In the meantime, we did our research and figured out that the owner moved out in June this year and has a tenant in the home for the past pne month, per the neighbors. Is this a valid lease, if there is one, under the PTFA? How can a lease signed one month before the auction be valid? The notice of default was first filed in 2008 per the register of deeds..
Thanks for any help...