They wrote about it on their blog.
https://blog.jetbrains.com/blog/2021/01/07/an-update-on-sola...
https://blog.jetbrains.com/blog/2021/01/08/january-8th-updat...
Summary: they have no idea what anyone is talking about, nobody has told them anything and there are no known issues with TeamCity. Later they did a blog post with security tips for locking it down but they're all pretty generic things that'd apply to any CI system.
These companies that are banning JetBrains and thus locking themselves out of some of the best software tools out there are now suffering the consequences of years of mass hysteria over Russia, largely promoted by the New York Times. Every time someone read or quoted the New York Times as an authority on something and did not receive major pushback, it was another brick in the wall that has now led to this.
It was all entirely predictable. In 2017 I wrote about an even more deceptive and malicious article in the New York Times on the topic of "Russian Twitter bots" and Brexit. The story was based on an academic paper that superficially made it seems like credible expertise, but was intellectual fraud from beginning to end.
https://blog.plan99.net/did-russian-bots-impact-brexit-ad66f...
After that I started compiling a list of stories I read about Russia that fell apart when fact checked. I gave up after doing sixteen of them because it was just endless.
https://blog.plan99.net/%D0%BF%D1%80%D0%B0%D0%B2%D0%B4%D0%B0...
The thread article starts by saying, "Most educated people believe that premier news outlets are inherently trustworthy". This is probably true but just makes it clear that education doesn't make people smart. The total unreliability of anything Russia-related in the "educated" press has been obvious for years. The only way for things to get better are for people to repeatedly attack the credibility of these outlets, in public, on any topic where they engage in deceptive practices, in front of the sort of decision makers who are now making snap anti-Russian decisions on the basis of prior articles.