I was named as a defendant on my ex spouses foreclosure - joined as he owes past due child support.

After I divorced me ex, he purchased a home and I just received a summons being named as a defendant on the foreclosure of the property he purchased. The note was entered into a month after our divorce was final. But the summons states that I "am being joined to foreclose any arrears that may have accrued subsequent to the closing of the loan being foreclosed herein and which are subordiante to the lien of the plaintiff's lien being foreclosed upon herein". I contacted the law firm who represents plaintiff (the bank) and they said I need to do nothing as I am listed as a defendant simply because of the child support lien. Does this seem correct? I do not have resources to afford an attorney and was going to respond with a letter but I do not know what to do. Thank you!!!