American gymnast Simone Biles, who won four gold medals last month at the Rio Olympics, defended herself against accusations of doping by a Russian hacker group. Biles, 19, said on Twitter that she had Attention Deficit Hyperactivity Disorder and had been taking medicines for it since she was a child. This was after the Russian hacker group called Fancy Bears broke into the World Anti-Doping Agency's database and released confidential medical data of American Olympians such as Biles and tennis players Serena and Venus Williams. The group alleged that American Olympians were allowed to consume banned substances by WADA during the Rio Olympics.

USA Gymnastics also defended Biles, saying that the 19-year-old "was approved for a therapeutic-use exemption" of certain drugs and "has not broken any drug-testing regulations, including at the Olympic Games in Rio".

WADA admitted that its database had been hacked. The hacker group accessed "confidential medical data – such as Therapeutic Use Exemptions delivered by International Sports Federations and National Anti-Doping Organizations – related to the Rio Games", WADA said in a statement. The group also "released some of the data in the public domain, accompanied by the threat that they will release more", the statement added.

“WADA deeply regrets this situation and is very conscious of the threat that it represents to athletes whose confidential information has been divulged through this criminal act,” said WADA Director General Olivier Niggli. “WADA condemns these ongoing cyber-attacks that are being carried out in an attempt to undermine WADA and the global anti-doping system,” he added.

After releasing the medical data in public, Fancy Bears had said on their website, "After detailed studying of the hacked WADA databases, we figured out that dozens of American athletes had tested positive. The Rio Olympic medallists regularly used illicit strong drugs justified by certificates of approval for therapeutic use."