hello, mozilla firefox is a webbrowser and no anti-virus solution, it does not contain a functionality to clean any infected system. however, the message you're referring to sounds quite suspicious - if this was a popup/overlay that showed up during browsing it is probably a scam and by malicious intent itself (since websites have no way to know about the security status of a device anyway). they might want to trick you into downloading compromised or infected versions of the software: [[Avoid and report Mozilla tech support scams]] so if you want to download firefox as your browser only do so through the google play store on your device or on desktop directly load firefox from its official website at mozilla.org !