Detecting different German with language filter

[fizzy92]

Hello,

I'm using the language filter that is installed with the Joomla package. I use detect Browsersetting to find out the language of new Users on my website. To my understanding the "Accept language" Header in the HTTP Request is getting analyzed to determine what kind of German the user is using. This is working as expected if the Header is set properly. For example:
In Chrome I can put in de-AT and de-DE as my language setting and the Browser puts in both languages in the "Accept language" header in the specific order that I can specify. The plugin takes whatever comes first and uses that as detected browser language. It does not matter if my actual display language is something else, which is fine. If there is no de-AT or de-DE in the header the plugin goes to the default language that is set in the plugin settings, which is de-DE in my case. So everything is working as intended so far.
In Firefox there is no differentiation between the different Germans. Therefore I can only see "de" in the "Accept language" header. The problem here is that, the plugin automatically detects "de-AT" even though only "de" is given und "de-DE" is suppose to be the default language.

Is there any workaround or fix for this issue?
The detection is crucial for my website and I hope someone can shine some light into this issue.
Thank you.