https://www.bleepingcomputer.com/news/security/over-4-000-backdoors-hijacked-by-registering-expired-domains/

Over 4,000 abandoned but still active web backdoors were hijacked and their communication infrastructure sinkholed after researchers registered expired domains used for commanding them.

Some of the live malware (web shells) was deployed on web servers of  high-profile targets, including government and university systems, ready to execute commands from anyone who tool control of the communication domains.