Firefox typically automatically checks for add-on updates after the browser itself is updated. If a Plugin is outdated or vulnerable, it will be listed at the top with an Update Now button to the right side of the page next to it.
By default, Firefox will automatically check for updates.
As a result, it will notify you if an update is available.
I am very conservative in my online habits and surprised by this occurrence. It was accompanied by a request to download and install which I didn't touch. 18.104.22.168 These "urgent update" pages are almost certainly Java Script redirects launched from malicious ads on the legitimate page you are viewing. You can middle-click any of the domains shown in the No Script dropdown list to view information about the domain.
The best way to avoid these is to impose restrictions on which sites are allowed to run Java Script in your browser: USA Today, Hard OCP, Neowin and Slickdeals were the pages. The idea is to allow the website itself and legitimate additional domains used by the site (Googlemaps, for example) while blocking other domains, such as advertising sites that may be serving malvertisements that redirect the browser.
A mobile version of Firefox is available for both Android and i OS devices.