Malwarebytes is the fourth cybersecurity firm targeted by the SolarWinds hackers, after Microsoft and FireEye confirmed that their systems were infiltrated by the same threat actor. The threat actor is tracked as StellarParticle (CrowdStrike), UNC2452 (FireEye), and Dark Halo (Volexity), and is likely a Russian-backed Advanced Persistent Threat (APT) group according to a joint statement issued by the FBI, CISA, ODNI, and the NSA earlier this month.
Source: https://www.bleepingcomputer.com/news/security/malwarebytes-says-solarwinds-hackers-accessed-its-internal-emails/