According to Avast, the database where the CCleaner hackers were collecting data from infected hosts was deleted on September 12, meaning information on previous victims is now lost to investigators and the number of computers infected with the second-stage backdoor payloads may be larger than initially believed. […]

from https://www.bleepingcomputer.com/news/security/info-on-ccleaner-infections-lost-due-to-malware-server-running-out-of-disk-space/