Norton forces shut-down Firefox during its patch installation

Just now Norton appears to have downloaded its update in the background when I was actively browsing, and without a warning, my Firefox browser was forced to shut-down. When the screen resumed, I was greeted with this error message and a restarted browser.

Question, I thought NS only installs its patch if it has my permission or only during the next restart, right? Plus, this is not even me who initiates the Live-Update, it was automated.

This has never happened to me before and I am very unsatisfied over the matter that Norton interfered with my browser activity without permission.