Supermicro has published a letter to its customers to explicitly state that no evidence of tampering was discovered in its hardware during a recent thorough internal review. An article from Bloomberg claimed that Supermicro products had been compromised by Chinese spy chips, which had then affected servers used by companies like Amazon and Apple.
https://www.notebookcheck.net/No-Chinese-spy-chips-found-in-Supermicro-internal-investigation.376566.0.html