Upgrade to IE11, even if you don't use it

Windows and IE are [still] deeply intertwined.

"There are many components that constitute the [IE] browser. Most of the components are part of the operating system..."

Applications other than Microsoft's IE can, and do, call on those components to display HTML or execute scripts. "If you aren't upgraded to the current version of IE, you won't be able to apply the current security updates. This could result in some Windows components not being serviced..."

http://www.computerworld.com/article/3021824/web-browsers/microsoft-upgrade-to-ie11-even-if-you-dump-our-browser.html 

Bottom line:   Update to IE11 (on systems which allow it; e.g., Windows 7) even if you "dump" it in favor of Firefox, Palemoon, Chrome, Opera [or some other alternative browser].