Avast-owned security application CCleaner was illegally modified by hackers. Some 2.27 million users were running the weaponized version 5.33 of the application. Avast: “A backdoor transplanted into a security product through its production chain presents a new unseen threat level which poses a great risk and shakes customers trust” An updated version of the software was released at September 12, 2017 – did not include any malicious code. The attack went undetected by any security company for four weeks.”]
Source: https://blog.morphisec.com/morphisec-discovers-ccleaner-backdoor