Jia Tan was the username used by a group — probably a state intelligence agency — on GitHub to try to attack the xz open source package. The effort aimed at trying to take over the project, and lasted for years. They managed to get a compromised package briefly into the unstable versions of some major Linux distros that created a backdoor in the openssh daemon and came close to being widely deployed across Linux servers, which would have been a very severe compromise of a huge range of systems. The account vanished when the compromise was discovered.

The user here is, as a joke, using the same name.

EDIT:

https://en.wikipedia.org/wiki/XZ_Utils_backdoor