Automatically adding text to post titles?

Hi there,

I want to automatically add the category of a post, to that post’s title. I am trying to emulate what they do at Mashable (see how they inserted [VIDEO] into the title in this article: https://mashable.com/2011/11/28/ups-package-not-delivered-scam/).

Using the code below works, except for one issue. It adds the categories to all menus on the page, as well. See demo site for example result: https://rmthis.tfcsouthsider.com/

So, my questions are:

1. Does anyone see a way to get this code to work?
2. Does anyone know a better way of automatically adding text to post titles?

Your help is much appreciated. Thanks.

function wpbeginner_cattitlerss($the_title) {
$postcat = "";
foreach((get_the_category()) as $cat) {
$postcat .= ' ['.$cat->cat_name . ']';
}
$the_title = $the_title.$postcat;
return $the_title;
}
add_filter('the_title', 'wpbeginner_cattitlerss');