Did you see this article? Advanced panel - Accessibility, browsing, network, updates, and other advanced settings in Firefox

By the way, Kaspersky is still protecting your computer even when the browser add-ons are disabled. What you are losing are the bonus features of those add-ons, such as marking bad sites in search results (and whatever else they are offering lately). The core function of quarantining or deleting dangerous files as you download them continues to run 24x7, since that feature hooks into the file saving process, no matter what application is doing the saving.