Nov. 30 2016: One of my security sources has flagged a Firefox vulnerability. The recommendation is to avoid using Firefox, until the next Firefox update. Currently the download is for version 50.0.1, make sure the version is something later than that. In the meantime use Chrome, Safari, or another non-Firefox based browser.
You can see the details at https://www.wordfence.com/blog/2016/11/emergency-bulletin-firefox-0-day-wild/