pluggable.php

function wp_clear_auth_cookie() {
  do_action('clear_auth_cookie');

	setcookie(AUTH_COOKIE, ' ', time() - 31536000, ADMIN_COOKIE_PATH, COOKIE_DOMAIN);
	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, ADMIN_COOKIE_PATH, COOKIE_DOMAIN);
	setcookie(AUTH_COOKIE, ' ', time() - 31536000, PLUGINS_COOKIE_PATH, COOKIE_DOMAIN);
	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, PLUGINS_COOKIE_PATH, COOKIE_DOMAIN);
	setcookie(LOGGED_IN_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
	setcookie(LOGGED_IN_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);

	// Old cookies
	setcookie(AUTH_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
	setcookie(AUTH_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);
	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
	setcookie(SECURE_AUTH_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);

	// Even older cookies
	setcookie(USER_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
	setcookie(PASS_COOKIE, ' ', time() - 31536000, COOKIEPATH, COOKIE_DOMAIN);
	setcookie(USER_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);
	setcookie(PASS_COOKIE, ' ', time() - 31536000, SITECOOKIEPATH, COOKIE_DOMAIN);
}