BleepingComputer.com: Delay in Typing

I am a Wikpedia editor and about a year and a half ago I encountered a problem where when I type something in the edit box, it would take a second before the words actually appeared on the screen. This only happens in wikpedia. So I scanned with Malwarebytes and got a malware and quarantined it. After that the issue was gone. About a week ago the problem came back. But I don't know if it's malware again, because Malwarebytes and Avast couldn't catch it. Please help me get rid of this annoying problem.