Temporary fix for unblocking unsigned xpi's in release Firefox versions (with other defaults).

Firefox\config.js

//
try {
    Components.utils.import("resource://gre/modules/addons/XPIProvider.jsm", {}).eval("SIGNED_TYPES.clear()");
    Components.classes["@mozilla.org/toolkit/crash-reporter;1"].getService(Components.interfaces.nsICrashReporter).submitReports = false;
} catch(ex) {}

// Disable extension signature check
pref("xpinstall.signatures.required", false);

// Disable checking if firefox is default browser
lockPref("browser.shell.checkDefaultBrowser", false);

// UserAgent override
// pref("general.useragent.override", "Mozilla/5.0 (Windows NT 6.3; rv:50.0) Gecko/20100101 Firefox/50.0");

// Disable auto-updates
//pref("app.update.enabled", false);
// Make absolutely sure it is really off
//pref("app.update.auto", false);
//pref("app.update.mode", 0);
//pref("app.update.service.enabled", false);
//pref("browser.search.update", false);

// Prevent closing dialogs
lockPref("browser.showQuitWarning", false);
lockPref("browser.warnOnQuit", false);
lockPref("browser.tabs.closeWindowWithLastTab", false);
pref("browser.tabs.warnOnClose", false);
pref("browser.tabs.warnOnCloseOtherTabs", false);

// Disable Add-ons compatibility and updates checking
clearPref("extensions.lastAppVersion");
pref("extensions.update.enabled", false);
pref("extensions.update.notifyUser", false);

// Disable plugin checking
//lockPref("plugins.hide_infobar_for_outdated_plugin", true);
//clearPref("plugins.update.url");

// Don't show "know your whatever" on first run
lockPref("browser.rights.3.shown", true);
lockPref("browser.feeds.showFirstRunUI", false);
lockPref("browser.privatebrowsing.dont_prompt_on_enter", true);
lockPref("browser.newtabpage.introShown", true);
pref("browser.startup.homepage_override.mstone", "ignore");
pref("general.warnOnAboutConfig", false);

// Show empty pages on startup and on new tabs
//pref("browser.startup.page", 0);
//pref("browser.newtabpage.enabled", false);

// Don't collect data
pref("geo.enabled", false);
//pref("privacy.donottrackheader.enabled", true);
pref("beacon.enabled", false);
pref("browser.search.suggest.enabled", false);

// Disable all data upload telemetry/health/crash
lockPref("toolkit.crashreporter.enabled", false);
lockPref("datareporting.healthreport.service.enabled", false);
lockPref("datareporting.healthreport.uploadEnabled", false);
lockPref("datareporting.policy.dataSubmissionEnabled", false);
lockPref("datareporting.healthreport.about.reportUrl", "");
lockPref("toolkit.telemetry.archive.enabled", false);
lockPref("toolkit.telemetry.prompted", true);
lockPref("toolkit.telemetry.enabled", false);
lockPref("toolkit.telemetry.unified", false);

// Browser Console command line
lockPref("devtools.chrome.enabled", true);

// Don't ask for remote debugger connection
pref("devtools.debugger.remote-enabled", true);
pref("devtools.debugger.prompt-connection", false);

// Don't allow sites to override context menu handler from JavaScript
//pref("dom.event.contextmenu.enabled", false);

// Remember downloaded files until browser exit
pref("browser.download.manager.retention", 1);

// Don't secondguess prefix/sufix in URLs
pref("browser.fixup.alternate.enabled", false);

// Always show protocol prefix
pref("browser.urlbar.trimURLs", false);

// Security
pref("browser.xul.error_pages.expert_bad_cert", true);
//pref("browser.safebrowsing.enabled", false);
//pref("browser.safebrowsing.malware.enabled", false);
pref("social.enabled", false);
pref("social.remote-install.enabled", false);

// Use directory request for downloads
pref("browser.download.useDownloadDir", false);

// Don't open new tabs automatically (use middle-click instead)
pref("browser.link.open_newwindow", 1);
pref("general.autoScroll", false);

// Extension mods
//pref("extensions.blocklist.enabled", false);
//pref("extensions.pendingOperations", false);

// Locale defaults
pref("intl.charsetmenu.browser.cache", "windows-1251, UTF-8");
//pref("intl.charset.default", "UTF-8");

// Enable some HTTP mods
//pref("network.http.pipelining", true);
//pref("network.http.pipelining.max-optimistic-requests", 2);
//pref("network.http.proxy.pipelining", true);
//pref("network.http.max-persistent-connections-per-server", 4);
pref("network.http.request.max-start-delay", 2);
//pref("network.http.redirection-limit", 10);

// Optimize memory consumption
//pref("browser.cache.memory.max_entry_size", 51200);
//pref("browser.cache.memory.capacity", 5120);
//pref("browser.sessionhistory.max_total_viewers", 1);
//pref("browser.sessionhistory.max_entries", 10);
//pref("image.mem.min_discard_timeout_ms", 10000);
//pref("image.cache.size", 52428800);

// Allow memory trimming on minimization
pref("config.trim_on_minimize", true);

// Maximum entries in history
pref("places.history.expiration.max_pages", 2000);

// Disable background link prefetching
pref("network.prefetch-next", false);
pref("network.http.speculative-parallel-limit", 0);

// How many charsets are cached (default: 5)
//pref("intl.charsetmenu.browser.cache.size", 2);

// Accelerate browsing
//pref("browser.display.show_image_placeholders", false);
pref("browser.tabs.animate", false);
//pref("gfx.direct2d.force-enabled", true);
//pref("gfx.font_rendering.directwrite.enabled", true);
//pref("layers.acceleration.force-enabled", true);
//pref("content.notify.backoffcount", 5);
//pref("content.notify.ontimer", true);
//pref("content.interrupt.parsing", true);
//pref("content.notify.interval", 500000)

Firefox\defaults\pref\config-prefs.js

pref("general.config.obscure_value", 0);
pref("general.config.filename", "config.js");