Ever since I updated CCleaner to v5.43.6522, I've noticed a possible bug in regards to cleaning files from Internet Explorer 11 on my Windows 8.1 laptop. (The version of IE I'm using is 11.0.9600.19003)
Whenever I clicked "Run Cleaner" it would prompt me to close IE in order to clean the files. However, the program was already closed and still gave me the prompt. Whether I clicked Yes or No, it would always skip cleaning IE's Temporary Internet Files, History, and Cookies despite them being checked in their respective tick-boxes. At this point, I decided to figure out what was causing this to happen, or otherwise diagnose the problem. I restarted my computer and logged back in and decided to start up CCleaner before opening IE again. Surprising enough, it seemed like the problem went away and cleaned the Temporary Files, History, and Cookies like it normally would when checked. After cleaning, I opened IE again for a bit and closed the program. When I went back to use CCleaner with the same tick-boxes checked like last time, however, the problem came back again. I repeated the same thing a second time later on with the same results. Thus, I believe I figured out what's causing this bug: If you run CCleaner before opening Internet Explorer, it will always clean as intended. However, if you open CCleaner after using Internet Explorer (regardless if you cleaned IE or not beforehand) it will always skip cleaning Temporary Internet Files, History, and Cookies. The temporary solution this problem is restarting your computer, unless there's another solution to this that I'm not aware of.
Hopefully this bug can be fixed in the near future