Scammers are getting more sophisticated. In this case sounds like the scammer posed as a potential renter, found out the open house details, then set up their own fake ad on an alternative platform, directing would-be renters to the actual open house. Then they took the application fee, first and last month's rent and deposit from potential renters by posing as the landlord.

Normally people can avoid rental scams by ensuring they see the property in person but this scam allows for that. Now people are going to have to be even more vigilant to ensure they give a cashiers check in person to the actual property manager.