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Here is what the download button now looks like when a download has been flagged by download protection: In addition to the new categories described above, we have made improvements to the user interface to make it easier for users to notice and understand these warnings. You may want to double-check the address of the site where you downloaded this file and proceed with caution. For example, if you are looking to download a new version of Firefox or a popular software package such as VLC and get this warning, it is possible that you have been tricked into downloading a malicious file from a phishing site which has not yet been identified as such by the Google Safe Browsing service. The purpose of this warning is to draw users’ attention to the fact that this may not be the download they think it is. The second category, uncommon downloads, covers downloads which may not be malicious or unwanted but that are simply not commonly downloaded. It is usually best to avoid this kind of software since it could (for example) collect your personal information without your consent and use techniques to make it difficult to uninstall. The first new category, potentially unwanted software, is meant to flag software that makes unexpected changes to your computer, as explained in the Google policy. Thanks to Google’s expansion of their Safe Browsing service, Firefox 48 now extends our existing protection to include two additional kinds of downloads: potentially unwanted software and uncommon downloads.
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Protection against malicious downloads was added in Firefox 31 on Windows and in Firefox 39 on Mac and Linux.
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