BAKU, September 13. /TASS/. US titled tennis stars Serena and Venus Williams had a special therapeutic permission for taking banned performance enhancing drugs, the International Tennis Federation’s (ITF) told TASS commenting on the recent hackers attack on the global Anti-Doping Administration & Management System (ADAMS).

Fancybear.net web portal of hackers announced earlier that it hacked the ADAMS and leaked documents proving that the World Anti-Doping Agency (WADA) allowed US tennis stars Serena and Venus Willams as well as US four-time Olympic Champion in gymnastics Simone Biles taking banned performance enhancing drugs.

"The ITF was notified by WADA earlier today that ADAMS, their anti-doping database, had been hacked and that copies of Therapeutic Use Exemption certificates have been posted on-line," the ITF said in its statement to TASS. "We are working with WADA to establish the nature and extent of this breach of security."

According to the information posted on the hackers’ website "Serena Williams, world's top tennis player, is taking oxycodone and hydromorphone (opioids), prednisone, prednisolone, and methylprednisolone as well."

"Her sister Venus Williams is used to take prednisone, prednisolone, triamcinolone and formoterol," according to Fancybear.net web portal.

Commenting on the allegations, the ITF said in its statement that "If you have a medical condition that requires Use of a medication or other product containing a substance or method that is on the 2016 Prohibited List, a Therapeutic Use Exemption (TUE) is required."

"A TUE permits you to use the prohibited medication or method without committing an Anti-Doping Rule Violation, providing that all such use is in accordance with the conditions of the TUE," the statement said. "Both (Serena and Venus Williams) were granted a TUE."

The International Olympic Committee (IOC) confirmed to TASS earlier in the day that ADAMS had been hacked, but all athletes mentioned in the information posted in the hackers’ web page tested positive for performance enhancing drugs at the 2016 Summer Olympics in Brazil last month.

"We cannot comment on documents that have been illegally obtained from the ADAMS system," the IOC told TASS. "The IOC strongly condemns such methods which clearly aim at tarnishing the reputation of clean athletes."

"The IOC can confirm however that the athletes mentioned did not violate any anti-doping rules during the Olympic Games Rio 2016," the statement from the IOC added.