downloaded the application from https://www.waterfox.net.
followed the instructions . when I am trying to open the application from Finder getting the below error :
“Waterfox” can’t be opened because Apple cannot check it for malicious software.

The application hasn't been "notarized", but I wouldn't call it a bug.
Apple now requires applications to be submitted to them for a virus check and approval ("notarized") by default, even from recognized developers. But if you trust the developer you can just right click the app and choose "open" and then "open anyway".
See the bottom of this page: https://support.apple.com/en-us/HT202491
Which version?
https://redd.it/fa773y mentions _Waterfox Classic_ but not a version.
Key points:
… Now that I’ve got some help I’ll dive in and see if I can get notarisation working for Classic too.
👍
@MrAlex94 would you like to make sticky your comment in Reddit?
(Mine is unstuck; I can't stick yours.)
Most helpful comment
The application hasn't been "notarized", but I wouldn't call it a bug.
Apple now requires applications to be submitted to them for a virus check and approval ("notarized") by default, even from recognized developers. But if you trust the developer you can just right click the app and choose "open" and then "open anyway".
See the bottom of this page: https://support.apple.com/en-us/HT202491