NoScript suddenly removed after Firefox crash

[chino8]

I was watching a video on Youtube when suddenly Firefox crashed. I tried to reopen Firefox but a message appeared "...that one instance of Firefox is already running". So I opened the Task Manager. The moment i did that, three unknown programs started running. They were suspicious, so I closed them. I didn't find firefox.exe in the Processes. Then I ran Firefox again and it opened. I quickly noticed that the NoScript icon was gone. When I checked the Firefox Extensions, all installed extensions were gone but the CompareItApplic which wasn't there before (the date of installation was the day when all of this accured). I removed and uninstalled CompareItApplic from Firefox Extensions and uninstalled it from Windows 7 control panel. I cleared all history and restarted Firefox from Troubleshooting information menu. Then I ran Spybot which didn't find anything noticeable and then Malwarebytes Anti-Malware which didn't find anything either. Now everthing seems normal. The only problem is that I have to reinstall all the extensions to the Firefox and I lost the Noscript whitelist.

Did anyone have this issue?

[barbaz]

Your system has been infected with malware, NoScript being removed is the least of your problems.

Please scan your system for malware using both your antivirus and a tool like Malwarebytes Anti-Malware (the free version will do). If that does not get it try also AdwCleaner.

[Thrawn]

S/he already tried Malwarebytes. But I agree, this sounds like malware infection. If all seems quiet again, then chances are that the malware has gone to ground and it's time for a system reformat + restore.