Kaspersky usually takes a while to release updates after a Firefox version update. It may be available in a week or two, I haven't checked their latest announcement. (I'm assuming Kaspersky because your plugin list shows the Content Blocker Extension and Online Banking Extension plugins.)

However, the function of the Kaspersky Protection extension probably is less than you imagine. The main Kaspersky program intercepts disk writes to prevent harmful downloads, and the filtering features intercepts every web requests and checks it before passing it on to Firefox. Those should still be working even if the extension is disabled. The extension seems to be mostly used for the Protected Browser mode feature. Do you use this feature often?

I overlooked something which could be an alternate explanation. If you check the explanation on the Add-ons page, why is the extension disabled? You can view that using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then scroll down on the right side (disabled extension are at the bottom of the list).

If the Add-ons page indicates the problem is that the extension is not verified:

Firefox 43+ requires that extensions be digitally signed by Mozilla. This article has more information: Add-on signing in Firefox. Kaspersky is said to be working on making that happen.

Until it does, you can make a global exception to the signing requirement (there's currently no way to only make an exception for specific extensions).

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste xpin and pause while the list is filtered

(3) Double-click the xpinstall.signatures.required preference to switch it from true to false -- note that this is for Firefox 43-45 only