Elon Musk's party habits made him a dream target for Russian spies (msn.com)

>Buma told this to Zweites Deutsches Fernsehen, a German TV channel, in a documentary. In an interview with ZDF Buma revealed that Musk and billionaire Peter Thiel both were targeted by Russian intelligence agents.

This seems to be a primary source:

https://www.zdf.de/nachrichten/politik/trump-musk-putin-100.... (in German)