CCleaner cannot erase Firefox cache when this cache located in custom folder. If Firefox internet cache location changed (browser.cache.disk.parent_directory = d:\ffcache) , then CCleaner dont detect and clear cache.
CCleaner 5.10
Win 7 SP1 64bit
Firefox 41.0.1
You can manually tell CCleaner to clean: d:\ffcache
Part 1: Enabling Custom Cleaner:
1. Open CCleaner
2. Scroll all the way to the bottom and under 'Advanced' tick the box titled: Custom Files and Folders
Part 2: Including The Path To Clean:
3. Click: Options > Include
4. Click: Add > File or Folder
5. Browse to: d:\ffcache
6. Click OK twice.
Now whenever you run CCleaner it will clean d:\ffcache