A few final notes/observations.
First, it is not unusual that there are prior unpaid taxes on foreclosed property. What is unusual is that an escrow company/title insurance company "missed" them.
Second, you (personally) can't use the excuse "I was so busy...this was my first home purchase...you can't expect me to check out everything." That IS your responsibility. Fortunately, you delegated that responsibility to your escrow company/title insurance company/closing attorney. So someone in that mix is going to be responsible for the taxes IF the deed you received transferred the property subject only to current year taxes. And it is entirely possible the selling bank will ultimately be responsible for the taxes IF their deed conveyed it to you by warranty deed subject only to current year taxes. But that is for the escrow/title company to pursue...not you.
Third...I don't know that the real estate agent bears any responsibility in this mess...clear title is outside their area of expertise.
Finally...by placing the Bank/title co/closing atty on notice of their mistake and giving them a reasobnable chance to fix it serves another purpose...if they fail to do so and it causes you additional grief/expense, then you can sue them for the initial damages of the taxes and, MORE IMPORTANTLY, for bad faith. And THAT's where the real money is
My predictions are A) the back taxes will be paid B) by someone other than you.