Starting today, Mozilla has begun rolling out Firefox 48. Notably in this release, security has been increased with regards to downloading software. Firefox will now warn you when you attempt to download files that are classified by Google’s Safe Browsing service as either ‘potentially unwanted software’ or ‘uncommon downloads’.
Potentially unwanted or uncommon downloads will now show a yellow exclamation mark over the download button, however, when you open the download menu you will still be offered the normal open folder button. When downloading known malware, a red exclamation mark will hover over the download button and when you open the download menu the open folder icon will be switched with a delete file button but this can be overridden by right clicking the item and choosing another action from the contextual menu.