Unable to save router's .cfg file in Firefox

[John Gray]

Having logged on to my router's admin interface in Firefox I wish to save the router's .cfg file (about 12k) to my hard disk. This was quite routine a few years ago, when I last needed to do it after a change.

Apparently Firefox (now?) treats this Save/Backup action as a Download, and refuses to do this, treating the file as a "potential security risk".

I've tried saving the .cfg file as a .txt file, but annoyingly the router software always appends ".cfg" if this isn't already present.

Has anyone any idea how to force .cfg files to be treated as benign?
I've explored Tools -> Settings -> General -> Applications, but can't see how to Add a Configuration files entry...

[Leif]

Does https://support.mozilla.org/en-US/questions/1419499 help?

[John Gray]

Yes, it does! Thanks!
A different article suggesting messing with a Windows Attachment Manager registry entry didn't do anything...