Are there "fake" update messages from malware?

During Firefox use today, a popup window came into view urging me to update my current version of Firefox. I was engaged with another chore and did not... and then forgot I had the popup and closed Firefox without acting upon it. I do not have updates set to update "automatically" but rather to inform me of the needed updates. I have "Block popup windows" activated in Firefox. I am running Firefox v. 25.0.1 The popup looked like the usual Firefox browser update pop-up, including indications that the update offered enhancements in security. Remembering that I was asked to update - I searched (in vain) for a button in one of the menus saying "Search for Updates" or "Update Firefox." That button is seemingly no longer available. The popup did not reassert itself. I finally resorted to going to "Firefox Health Report" and searching through there to find the report on my present version of Firefox, and then to request info. I was told that my *current version of Firefox is the latest available. You are up to date." So - was the popup created by malware? Is there a way for malware to "pretend" to be an official Firefox update pop-up window? I have clicked to update using similar windows in the past - have I installed a malware version or an official version of Firefox? How can I tell them apart? Thank you