The release of confidential athlete records by a Russian hacker group includes data about Serena and Venus Williams, showing use of prohibited substances for which Therapeutic Use Exemptions (TUE) appear to have been obtained.

In addition to the Williams sisters, basketball player Elena Delle Donne and gymnast Simone Biles had their World Anti-Doping Agency records released. A WADA spokesperson told wire agencies that none of the athletes whose data was released committed a violation.

The hacker group, claiming to expose "tainted victories" and "licenses to doping" with regard to athletes from the United States, obtained documents showing that Serena and Venus were given TUEs that allowed the use of substances prohibited by the anti-doping code.

The International Tennis Federation confirmed in a statement that the TUEs were authentic documents.

Serena was granted approval for oxycodone, hydromorphone, prednisone, prednisolone and methylprednisolone in 2010, 2014 and 2015. The first two are medically defined as opioid painkillers, and are banned in the anti-doping rules because they’re labeled as narcotics. The second two are medically defined as corticosteroid anti-inflammatories, a portion of which are generally banned in competition.

Several of the TUEs were given at times when Williams was not competing, including in 2010 when she missed time with a foot injury and pulmonary embolism. However, a TUE for prednisone was granted a year ago, during the second week of the French Open.

Venus approved for the following substances from 2010-2014: prednisone, prednisolone, triamcinolone and the generic form of the asthma inhaler symbicort. The first two are medically defined as corticosteroid anti-inflammatories, a portion of which are banned in competition, and the third is defined an antibiotic.

Venus, who was diagnosed with Sjogren's syndrome in 2011, released a statement.

“I was disappointed to learn today that my private, medical data has been compromised by hackers and published without my permission,” she said. “I have followed the rules established under the Tennis Anti-Doping Program in applying for, and being granted, therapeutic use exemptions.

"The applications for TUEs under the Tennis Anti-Doping program require a strict process for approval, which I have adhered to when serious medical conditions have occurred. The exemptions posted in the hacked report are reviewed by an anonymous, independent group of doctors, and approved for legitimate medical reasons.

“I am one of the strongest supporters of maintaining the highest level of integrity in competitive sport, and I have been highly disciplined in following the guidelines set by WADA, USADA the ITF and, collectively, the Tennis Anti-Doping Program."

WADA confirmed and condemned the attack on its records system, saying investigations showed that it originated in Russia. The Russian government has denied involvement. Following revelations of state-sponsored doping in Russia, Russian athletes in several sports—no tennis players—were barred from competing at the Rio Olympics.

The WTA tour and USADA also issued statements against the attack on the WADA database.