I’m getting this error on PHP 8.0

Fatal error: Array and string offset access syntax with curly braces is no longer supported in /var/www/skatox/htdocs/wp-content/plugins/promote-mdn/includes/functions.php on line 87

In my site i get this html code:
<div id=&quot;promote_mdn_widget-3&quot; class=&quot;widget widget_promote_mdn_widget&quot;>
And create some problem on the template…

https://www.ads-software.com/plugins/promote-mdn/