We recently determined that older versions of our Piriform CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191 had been compromised. We estimate that 2.27 million people used the affected software. We resolved this quickly and believe no harm was done to any of our users. This compromise only affected customers with the 32-bit version of the v5.33.6162 of CCleaner and the v1.07.3191 of CCleaner Cloud. No other Piriform or CCleaner products were affected. We encourage all users of the 32-bit version of CCleaner v5.33.6162 to download v5.34 here: download. We apologize and are taking extra measures to ensure this does not happen again.
Issue Summary: Our new parent company, the security company Avast, determined on the 12th of September that the 32-bit version of our CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191 products, which may have been used by up to 3% of our users, had been compromised in a sophisticated manner. Piriform CCleaner v5.33.6162 was released on the 15th of August, and a regularly scheduled update to CCleaner, without compromised code, was released on the 12th of September. CCleaner Cloud v1.07.3191 was released on the 24th of August, and updated with a version without compromised code on September 15. The compromise could cause the transmission of non-sensitive data (computer name, IP address, list of installed software, list of active software, list of network adapters) to a 3rd party computer server in the USA. We have no indications that any other data has been sent to the server. Working with US law enforcement, we caused this server to be shut down on the 15th of September before any known harm was done. It would have been an impediment to the law enforcement agency’s investigation to have gone public with this before the server was disabled and we completed our initial assessment. Between the 12th and the 15th, we took immediate action to make sure that our Piriform CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191 users were safe - we worked with download sites to remove CCleaner v5.33.6162, we pushed out a notification to update CCleaner users from v5.33.6162 to v5.34, we automatically updated those where it was possible to do so, and we automatically updated CCleaner Cloud users from v1.07.3191 to 1.07.3214.
We are continuing to investigate how this compromise happened, who did it, and why. We are working with US law enforcement in their investigation. A more technical description of the issue is on our Piriform blog at: www.ccleaner.com/news/blog. Again, we sincerely apologize for this and are committed to making sure nothing similar happens again. We encourage any user of the 32-bit version of CCleaner v5.33.6162 to download the latest version of Piriform CCleaner found here: www.ccleaner.com/ccleaner/download/standard.