The highest institution in football has been inquiring for a year
FIFA punished Madrid and Atlético Madrid (just like they punished Barça over a year ago) for breaking the rule about signing under 18 foreign players. The organization made it official this Thursday, when FIFA's Disciplinary Comitee, presided by Claudio Sulser, published the decision taken. It is the same that was taken against Barça: sanction and a ban with no right to sign any players in the next two transfer windows.
According to FIFA's communicate, both clubs have been punished with a transfer ban which prevent them to register any players at national and international levels for the next two complete and consecutive registration periods for having broken the articles 5,9, 19 and 19 bis, as well as appendices 2 and 3 of the Regulations on the Status and Transfers of Players. This ban DOES NOT apply for the current registration period, because it was open before the decision was made public. It applies to both clubs in their entirety (except for women's football, futsal and beach soccer teams) and doesn't prevent them from releasing players.
Moreover, Atlético Madrid and Real Madrid have been respectively fined 900,000 Swiss Francs (around 820,000 euros) and 360,000 Swiss Francs (around 330,000 euros). FIFA also gave a 90-day period to both clubs so they sort out the situation of all minor players involved.