People consider Firefox as one of the best browser. Cyber crime is at its peak though. Some crypto extensions are never scanned for malwares before making them available for internet. Recently, chrome acted upon some crypto extensions and removed such malwares. FF is learning.
No matter how secure something appears to be, it's also in the users' best interest to make sure that they are careful while using it, especially when the time to use it for anything that has to do with funds comes. An extension is not just supposed to be installed when we don't trust the developer, especially on a PC we make use of and could easily be used to access our crypto wallet.