According to a company statement, the data leakage could affect approximately 2.27 million users.
Hackers managed to integrate malicious code into the versions released on August 15 and 24. As a result, computers sent IP addresses and a list of installed applications from the users' computers to a server located in the US. US authorities blocked access to the server on September 15; the developer together with Avast (which acquired UK-based Piriform back in July) are conducting an investigation.
Piriform noted that they have "quickly resolved the problem," and users are safe now.
"We found that older versions of our CCleaner 5.33.6162 and CCleaner Cloud 1.07.3191 were hacked; we quickly resolved the problem and believe that none of our users were hurt," the developer said in a statement.
The company said that specialists are taking all necessary measures to prevent this from happening again.
According to statistics, CClearner has been installed in computers more than 2 billion times.