Pressing an accent key (´ / ˇ) adds the character twice in most programs

Question

This might seem as duplicate of Pressing key with accent character makes it enter twice but it is not:

About three days ago, the issue started - I am using Slovak (Slovakia) keyboard, and the key for adding accents/diacritics (just left from backspace) acts strangely - it should "do nothing" upon pressing, and then when character key is pressed right after it, it should output that character with accent/diacritics.

However, in most programs, pressing it once results in immediately outputting the accent itself twice (which under normal circumstances happens when you press the key twice). This issue doesn't happen in Visual Studio or any program I make in it, and Pidgin, it seems to happen everywhere else (firefox, notepad, MS OneNote, Windows Explorer itself).

I am not aware of any software installations, driver changes or system updates between the time it worked properly and the time when it broke.

What could be the problem and how do I solve it?

Answer 1

Another possible cause seems to be a fake svchost process (which was pretty obvious on my x64 machine as it was a 32bit process) located in your user folder in AppData/Local/Temp. I first had to end the process from task manager, then end DCom service that kept the exe file open, then gain ownership of the fake svchost.exe file, and then i could delete it.

Answer 2

It appears I have found and solved the problem:

It seems to have been an effect/symptom of a process named Winmonitor.exe, which is a trojan/rootkit. It prevents antivirus to start/shuts it down immediately, but it can be killed from Task Manager (show processes from all users), and offcourse deleted. I was not specifically looking for it as the cause of my problem, but once I found and removed it, the accent key works as expected again.