Error message

I am getting the following error message on the frontend of my site. How do I fix this please?

Deprecated: strpos(): Non-string needles will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in /home2/xxxxxxx/xxxx/htdocs/wp-content/plugins/bento-expansion-pack/includes/update-checker/Puc/v4p4/Plugin/UpdateChecker.php on line 641