If you haven’t yet, now is the time to move to 13+. Asterisk 11 has been security only for the last year. This means no regular bugs have been fixed. Now no security bugs will be fixed. Essentially if someone discovers a vulnerability you will be exposed using 11.
If you are on a distro system you can change to a supported asterisk branch by running asterisk-version-switch
https://wiki.freepbx.org/display/PPS/Changing+Major+Asterisk+Versions+on+the+Fly
