My username was previously "NetherGranite", but I came back to the Mathematics Stack Exchange to find that it was replaced with a generic "user____". Trying to change it results in a prompt saying that one can only change their username every so many days. Should I take steps to secure my account? If so, what are those steps?
When you edited your profile to change your profile picture and copied it to all sites back on December 12, for some reason the Mathematics site thought you had changed your display name to blank and it triggered a reset to the default display name on that site. I've changed it back to your actual display name.