All extensions disabled due to expiration of intermediate signing cert

Open the browser console by hitting ctrl-shift-j

Copy and paste the following code, hit enter. Until mozilla fixes the problem you will need to redo this once every 24 hours:

    // Re-enable *all* extensions

    async function set_addons_as_signed() {
        Components.utils.import("resource://gre/modules/addons/XPIDatabase.jsm");
        Components.utils.import("resource://gre/modules/AddonManager.jsm");
        let addons = await XPIDatabase.getAddonList(a => true);

        for (let addon of addons) {
            // The add-on might have vanished, we'll catch that on the next startup
            if (!addon._sourceBundle.exists())
                continue;

            if( addon.signedState != AddonManager.SIGNEDSTATE_UNKNOWN )
                continue;

            addon.signedState = AddonManager.SIGNEDSTATE_NOT_REQUIRED;
            AddonManagerPrivate.callAddonListeners("onPropertyChanged",
                                                    addon.wrapper,
                                                    ["signedState"]);

            await XPIDatabase.updateAddonDisabledState(addon);

        }
        XPIDatabase.saveChanges();
    }

    set_addons_as_signed();

    async function set_addons_as_signed() {
        Components.utils.import("resource://gre/modules/addons/XPIDatabase.jsm");
        Components.utils.import("resource://gre/modules/AddonManager.jsm");
        let addons = await XPIDatabase.getAddonList(a => true);

        for (let addon of addons) {
            // The add-on might have vanished, we'll catch that on the next startup
            if (!addon._sourceBundle.exists())
                continue;

            if( addon.signedState != AddonManager.SIGNEDSTATE_UNKNOWN )
                continue;

            addon.signedState = AddonManager.SIGNEDSTATE_NOT_REQUIRED;
            AddonManagerPrivate.callAddonListeners("onPropertyChanged",
                                                    addon.wrapper,
                                                    ["signedState"]);

            await XPIDatabase.updateAddonDisabledState(addon);

        }
        XPIDatabase.saveChanges();
    }

    set_addons_as_signed();

what did I do wrong? (It's all Greek to me)

Apparently beta and nightly need to change `Components.utils.import` to `ChromeUtils.import`.

But anyways, don't use this now, use the semi-official fix of clicking on this link and letting it install: https://storage.googleapis.com/moz-fx-normandy-prod-addons/e...

This is the fix Mozilla has published to be installed via shield studies, but skipping the shield studies part. You can be sure it's not malicious because it is signed by Mozilla... and if your browser installed unsigned extensions you wouldn't be looking for this solution in the first place.

Go to "about:config" (in the url bar), search for and enable devtools.chrome.enabled, then hit ctrl-shift-j (or you can open it from Menu -> Web Developer -> Browser Console).