Hi All,
For now, until a fix is released, just rename updater.exe to updater.exe.OLD (Win 8.1 Pro 64bit here) in Program Files/CCleaner. As soon as I did this the startup item in Task Manager 'magically' disappeared. Also, be sure to sure to go to Task Scheduler and DISABLE the new task this latest version adds there.
Piriform, we already have enough 'Data Miners' to deal with every day. So, just do what we paid for you to do and that is to help keep our systems clean.
Thank you!