Landlord over charging for a section 8 tenant

I have a complex legal question regarding a landlord who has overcharged a section 8 tenant over a period of two years. The section 8 tenant is legally handicap/blind. During these two years the landlord has gradually raised the tenants rent several times. The tenant paid the increased rent each time, unaware of the section 8 rule that states all landlords that accept section 8 may NOT raise the rent. Also the tenant was unaware that paying the increased rent and not notifying the section 8 authorities would jeopardize eligibility. Let me reiterate that the tenant is legally handicap/blind and mistakenly did not know about these rules and was just paying the increase, as a honest tenant would. Who is legally in the wrong? What further steps can be taken on behalf of the tenant?