I tried installing 2 application lock softwares which were blocked and disinfected by Bitdefender after which hidden and system files can't be seen. (after the disinfection process is fully complete)
Before installing the softwares, I had checked on hidden items in the view tab and unchecked on "Hide protected operating system files" under Options -> Change folder and search options -> View
The 2 application lock softwares are:-
1. Free App Lock: http://www.freeapplock.com/
2. Smart-X AppLocker: https://download.cnet.com/AppLocker/3000-2653_4-10910060.html
I had installed the first software "Free App Lock" on Windows 8.1 while the "Smart-X AppLocker" I had installed on Windows 10 home (both Windows versions on different laptops).
In both the cases, hidden and system files can't be seen after disinfection. No matter what workaround or registry fix you do, the hidden and system files won't be displayed.
However, this lasts only temporarily. After a restart, you can again check on hidden items and uncheck on "Hide protected operating system files" after which hidden and system files can be seen.
I have encountered the same problem while installing some other softwares as well (will provide details if required). Even though this bug lasts temporarily, I felt that I should inform this over here on Bitdefender forum so that the bug gets fixed.
Thank you.