Mozilla nor the Firefox browser has no control of Plugins install and updates. Plugins are on your system and not installed in Firefox like Extensions and Themes (complete) are. Type about:plugins in Location (address) are to see where they are located on your system.

If you downloaded Flash Player for Windows from https://get.adobe.com/flashplayer/ then you need to uncheck the extras. The extras is not a issue for Mac OSX and Linux versions of Flash Player from this page.

You can download Flash Player (without any extras for Windows version) from https://www.adobe.com/products/flashplayer/distribution3.html however this page may be getting decommissioned for good this time on Sept 29, 2016.

sorry but this is no resolution, there was no option, that's why this is so absurd! it was an JUST AN update, no options to OPT-OUT! IT PLANTED ALL KINDS OF JUNK! It was supposed to be a clear UPDATE, THAT'S ALL!!!!! Adobe flash that's why I've been told to avoid these things like the plague~ well, LESSON LEARNED, AND GOOD BYE MOZILLA!!!! AGAIN!!!! and another thing, I've "removed" McAfee before... I'm too old to go into the registry for that again..... I've hit the "uninstall" icon, but guess what, there's more that is here to stay. there is a reason I do not do McAfee, Norton etc, I've made my choice and haven't had a problem yet.... probably will get a new computer (tomorrow, ha)

If you did not get a section to uncheck the extras before downloading on https://get.adobe.com/flashplayer/ then you may have a adblocker extension issue. Users with Adblock Plus extension have reported that the section of the page where you can uncheck the McAfee option is hidden by Adblock Plus.

This is one of the reasons why many helping out in support here use the https://www.adobe.com/products/flashplayer/distribution3.html link so Windows users do not get the extras they may get by chance by downloading from https://get.adobe.com/flashplayer/

As for how to uninstall McAffe http://www.wikihow.com/Uninstall-McAfee-Security-Center

Ok since you do not believe me in that you can uncheck the extras for Windows version on https://get.adobe.com/flashplayer/

Since I used Linux I changed my UA to a Firefox 47.0 UA on 32-bit Windows 7 to take a screenshot example of what you should see.

See image below, note the Optional offers part you can uncheck in middle.