This report is related to the one already posted but there is a little bit more information in it including some comments from Curtis Rogers the owner of GEDMATCH:
The DNA database used to find the Golden State Killer is a national security leak waiting to happen
It sounds like GEDMATCH are dealing with it though:
Rogers, who is not a computer programmer, did not offer details about what fixes GEDmatch had implemented. “I let the technical people work on it and I believe they have,” he said in an interview. He later emailed to say the site was “actively working to add more security measures based on the reported problems.”
Ney says he does not believe the genealogy site is secure. “How much effort does it take to secure a large website with a million plus in genetic data? I think it’s hard for anyone to do, the questions I have is whether a volunteer run effort is capable of having the manpower to handle it,” says Ney.