Robert2
1
Windows 10 Home version 1809 64-bit
Firefox Quantum 63.03 64-bit
CCleaner v5.49.6856
Whenever I “Run Cleaner”, I get the following message:
“Firefox needs to be closed to clean the Internet Cache.
Do you want CCleaner to close Firefox?”
The problem is I just closed Firefox and Firefox is no longer listed among the running apps.
This message never appeared before CCleaner last update.
Nergal
2
Make sure firefox isn't hiding in task manager's processes section. 97% of the time an addon is keeping firefox from fully closing
nukecad
3
Occasionally you can be too quick - and Firefox slow to fully close.
The cache in particular can sometimes take 5 to 10 seconds before it has closed. But disappears from task manager before that.
So if you're quick and try to clean it before it has fully closed you get that message.
Or as Nergal says some add on could be keeping it open.