While trying to download the latest CCleaner F-Secure marks download.piriform.com/ccsetup528.exe as malicious.
False positive I presume.
EDIT: removed hyperlink
Sorry for my reply (I also F-Secure user).
With such situations usually helpful transfer-URL to F-Secure SAS:
They able to re-rate/do response about situtation. With work days it can to take about day/two days.
With my situation - I also able to get block-page for this certain URL (as harmful/malicious-rated website).
But looks like that not all piriform (download.) resources/URLs marked as harmful.
At least: other solutions available; and previous CCleaner build also available by related URL.
But fresh build installer (your URL) and (at least - Pro trial installer also) blocked as harmful page.
Also I using CCleaner PRO (where available autoupdate feature) - so it will install fresh build (F-Secure do not trigger something and do not prevent downloading).
I think maybe detection (f/p blocking page as malicious) can be about bundle for first-try experience with Piriform/CCLeaner installer (previously it was with Google Chrome suggestion or/and plugins/addons for Chrome) - how I can to understand this is still can be there.
If I normally remember - time to time Piriform-downloading-resource marked as malicious page under F-Secure Security Cloud by somewhat reasons. Transferring URL to F-Secure SAS most likely helpful step.
Sorry for my reply.