Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.
You can't manually install plug-ins. many installers will only extract their files to a recognized browser's dir.
Did you simply extract firebird or use a installer?
If(you didnt use an installer)
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I'd delete your Firebird folder and use this web installer:
Firebird Web installer...