I have noticed that with the upcoming Firefox 32, which is currently in Nightly state, the browser will use Google's safe browsing database to check files you have downloaded from the Internet. For every executable file you download, Firefox will perform a check against the online database which is provided by Google. The current version of Firefox 31 also ships with a similar option, but it uses a local database and does not send any request to Google's sites. Firefox 32 will continue to use the local database, however, if the downloaded file isn't found in the local database, Firefox will send the information to Google. You might be interested in disabling this behavior due to privacy concerns. Here's how you can turn it off.