Cisco Talos initially recommended that reinstallation of Windows or returning to a time before the infection via backups was the only solution. Now it has doubled down on that advice, saying that it can "confirm that at least 20 victim machines were served specialized secondary payloads." And the gathered "information would be everything an attacker would need to launch a later stage payload that the attacker could verify to be undetectable and stable on a given system." Both Kaspersky and Cisco Talos believe that the attackers are Group 72, probably from China.
So contrary to the speculations of Piriform which stated that it stopped the infections before they started, it appears that the malware was actually highly successful. The only silver lining is that it was initially targeting high-value computers and not the average surfer.
CCleaner 5.33 was signed using a valid digital signature issued to Piriform. Now Avast has revealed that 32- and 64-bit payloads were included, with the former using a patched TSMSISrv.dll (originally VirtCDRDrv32.dll created by Corel), and the latter using a patched EFACli64.dll (originally part of Symantec Extended File Attributes used in its Internet Security product).
Your author is reinstalling Windows on all computers for which he is responsible, with Piriform products not being reinstalled, and recommends that everyone else do the same, unless they have suitable backups and use them promptly.
If reinstalling Windows is beyond you, you must do three things immediately:
1) Uninstall all Piriform products -- CCleaner, Defraggler, Recuva, and Speccy -- via Control Panel -> Uninstall a program.
2) Go to C:/Windows/Prefetch (you'll need to use an admin login) and delete all entries that start with "ccleaner" and also ones that have the format "ccsetupxxx" (there will be one for each version of CCleaner that was ever installed on your PC, e.g. "ccsetup533"). Then reboot.
3) Download, install, and run a full system scan with Malwarebytes (the free version is okay).