It's sad users are subjected to legalese and spyware has become the accepted norm among 'free and proprietary' services. If this were some random add-on developed by some nobody it would have been appropriately removed from mozilla services.
Protip: Firefox already has Google Safebrowsing for malware. All you really need is to block ads and malware domains with Ublock add-on and scan files with the virustotal website. If you still need this add-on, maybe you should reconsider your browsing habits.