For those that have recently downloaded or updated CCleaner for Windows on a 32-bit system, be sure to update immediately, as they unknowingly distributed malware for roughly a month. The VP from Piriform, the company that creates and distributes CCleaner, has released a blog post describing the incident.
Currently, they are not sure how the code appeared in the software, but they are conducting a thorough investigation.
Again, we would like to apologize for any inconvenience this incident could have caused to our clients; we are taking detailed steps internally so that this does not happen again, and to ensure your security while using any of our Piriform products. Users of our cloud version have received an automated update. For all other users, if you have not already done so, we encourage you to update your CCleaner software to version 5.34 or higher, the latest version is available for download here.