Bradley Wiggins and Chris Froome are among five British athletes whose medical records with the World Anti-Doping Agency have been leaked by computer hackers overnight.
As well as the two leading cyclists, golfer Charley Hull, rower Sam Townsend and rugby sevens player Heather Fisher are included in the second batch of athletes whose details have been made public by cyber espionage group 'Fancy Bears', which is believed to be from Russia.
There is no suggestion of any wrongdoing by any of the athletes.
WADA first fell victim on Tuesday when medical records relating to 'therapeutic use exemptions' (TUE) granted to certain athletes were leaked. TUEs can be issued to athletes who have an illness or condition which requires the use of medication that is on WADA's prohibited list.
The latest leaks suggest that Rio gold medallist Wiggins, who has never made any secret of the fact he suffers from asthma, has several TUEs for salbutamol, a substance commonly used in an inhaler.
Meanwhile, three-time Tour de France winner Froome has TUEs for prednisolone, a steroid that can be used for chest complaints.
American tennis stars Serena and Venus Williams and four-time 2016 gymnastics gold medallist Simone Biles were among those whose information was initially revealed earlier this week.
And on Thursday, WADA confirmed another leak of "confidential athlete data" had taken place - although it did not identify the athletes affected.
The statement read: "Fancy Bear' [aka Tsar Team (APT28)] have leaked another batch of confidential athlete data from WADA's Anti-Doping Administration and Management System (ADAMS).
"Similar to the leak that the Agency announced on 13 September, this time the group released the confidential athlete data of 25 athletes, from eight countries, into the public domain.
"The targeted athletes include 10 from the United States, five from Germany, five from Great Britain, one from the Czech Republic, one from Denmark, one from Poland, one from Romania, and one from Russia."
The organisation revealed that hackers had illegally gained access to its anti-doping administration and management system database via an IOC-created account for the Rio Games.
WADA director general Olivier Niggli said: "WADA is very mindful that this criminal attack, which to date has recklessly exposed personal data of 29 athletes, will be very distressing for the athletes targeted and cause apprehension for all athletes that were involved in the Rio 2016 Olympic Games.
"To those athletes that have been impacted, we regret that criminals have attempted to smear your reputations in this way and assure you that we are receiving intelligence and advice from the highest level law enforcement and IT security agencies that we are putting into action.
"Given this intelligence and advice, WADA has no doubt that these ongoing attacks are being carried out in retaliation against the Agency, and the global anti-doping system, because of our independent (Dick) Pound and (Richard) McLaren investigations that exposed state-sponsored doping in Russia.
"We condemn this criminal activity and have asked the Russian Government to do everything in their power to make it stop.
"Continued cyber-attacks emanating from Russia seriously undermine the work that is being carried out to rebuild a compliant anti-doping program in Russia.
"We still believe access to ADAMS was obtained through spear phishing of email accounts, whereby, ADAMS passwords were obtained enabling access to ADAMS account information confined to the Rio 2016 Games.
"We have no reason to believe that other ADAMS data has been compromised.
"WADA is reaching out to NADOs (National Anti-Doping Organisations) and IFs (International Federations) whose athletes are impacted by this new data release so they can provide them with the necessary support."
Froome says he has "no issues" with the leaks, pointing out he has spoken publicly about being granted TUEs before.
The 31-year-old told The Scotsman newspaper this summer that he had used TUEs twice during his career, in 2013 and 2014.
He said in a statement on Thursday: "I've openly discussed my TUEs with the media and have no issues with the leak which confirms my statements.
"In nine years as a professional I've twice required a TUE for exacerbated asthma, the last time was in 2014."