On it goes.The Russian cyber-espionage group Fancy Bears had promised to publish more confidential records of more athletes, obtained by hacking into the World Anti-Doping Agency’s databases. And last night they were good to their word, posting the confidential medical records of over a dozen more top athletes, including the British cyclists Bradley Wiggins and Chris Froome, showing the banned substances for which they had received a therapeutic use exemption (TUE). It followed the first leak of information detailing the TUEs Serena and Venus Williams and the gymnast Simone Biles had received. Wiggins and Froome have defended their use of TUEs, while the Williams sisters’ and Biles’ insistence that they had done nothing wrong has been staunchly backed by Wada and the tennis and gymnastics authorities.

Nonetheless, on social media questions about whether there is more here than meets the eye have been winging their way round the carousel. Some have doubted whether Serena Williams needed to take powerful medication such as prednisolone, methylprednisolone, hydromorphone, oxycodone and prednisone, for instance, while others have asked what the Fancy Bears data says about TUE use and how widespread it may be.

When it comes to the Williams sisters, however, one of the world’s top anti-doping experts tells the Guardian that the Fancy Bears data suggests no indication of wrongdoing. “The first thing that struck me was that nothing struck me,” says Richard Ings, who as a former president of the Australian Anti‑Doping Agency and senior executive of the ATP tennis tour is better qualified than most to judge. “Serena, for instance, had exactly the sort of medication – often for very short periods – you would expect for soft tissue injuries and was granted approval.”

But can we trust the process? In tennis, at least, Ings believes we can. “There is no doubt that TUEs can be abused,” he says. “It’s like any other aspect of anti-doping. You have anti‑doping agencies that tip off athletes before testing and you have anti-doping agencies that have TUE policies that are flexible at best. But tennis has an independent medical review board, which involves three doctors reviewing each TUE request from a player’s physician and – where appropriate – granting their usage with strict limitations.”

The Williams sisters and Biles aside, the wider question of whether widespread TUE usage is appropriate is one that is increasingly debated within anti-doping and sports science circles. The respected sports scientist Ross Tucker, for instance, believes that what started out as a legitimate practice – the idea that athletes with asthma, say, getting TUEs so they could negate the disadvantages they faced – has been corrupted. “I would consider banning all TUEs in competition,” Tucker tells the Guardian. “I know it is a hard-line stance. But what would be the downside if people with asthma cannot compete? Conceptually to me, that is fine. Because unfortunately the efforts to be inclusive with people who have valid medical issues have created a loophole that is being exploited by sophisticated dopers.”

Tucker points to the high use of corticosteroids, which are given to athletes to help them breath better yet can also be performance-enhancing. “If they were banned, unfortunately you would end up discriminating against people with asthma,” he says, “but, if you define asthma as a breathing disorder which prevents you from accessing your maximum capacity, you could argue that EPO should be legal because people don’t have high blood values too.”

Then there is the rumoured widespread use of cortisone, especially in cycling, to reduce weight while maintaining power, something Tucker calls the “holy grail” in the sport. “It’s an anti-inflammatory but it works because it negates the inflammatory pain that you normally get when you exercise and so there is no signal to back off.” He points out a further worrying issue with TUEs: in the past some athletes, such as Lance Armstrong, have been allowed TUEs retrospectively to escape possible bans, as the American did after testing positive for corticosteroids in 1999.

Some, like the triathlete Jodie Swallow, have called for all TUEs to be made public. Yet that raises privacy concerns. “If you have a female athlete going through IVF – why should the world know such a private issue,” one figure in anti-doping told the Guardian.

Ings concurs. “I know of athletes with hepatitis who are taking low doses of steroids to help control it and even athletes with cancers,” he says. “All sorts of things you don’t want on a front page of a Russian website.”

Ings believes the Fancy Bears hack is “an extension of a political beat-up from disgruntled people in Russia” which is clearly targeting Wada. “It’s trying to draw the conclusion that Wada is complicit in allowing athletes to dope to deflect from the fact that Russia was complicit in allowing athletes to dope,” he says. “This is not about corruption in Wada. It is about compliance and competency. I don’t think Wada has anywhere near the bandwidth to review all these TUEs and to make sure they are being applied properly.”

He calls for much more public information by sport and country about which and how many TUEs were received, approved, dismissed – and a proper compliance framework to audit the system. Tucker, who is a stronger critic of the status quo, concurs. “People who have asthma are told to start swimming, because it forces them to breathe in a controlled way and it helps symptoms, so the fact so many swimmers have asthma is not an indication of something dodgy and nefarious,” he says, “but we don’t know because there is no baseline data.

“Imagine if we knew how many swimmers are asthmatic by country? Or, say, endurance runners? Or which training groups were all on it? It would help us understand whether the use of TUEs is getting out of hand.”