Last updated: 20210214
If you get the error message when sending a message in Contact Form 7 on your WordPress:
Deprecated: get_option was called with an argument that is deprecated since version 5.5.0! The “blacklist_keys” option key has been renamed to “disallowed_keys”. in /wp-includes/functions.php on line 5143
Then simply do this:
I was able to remove this error by changing the following at contact-form-7\modules\disallowed-list.php, line 51:
$mod_keys = trim( get_option( 'blacklist_keys' ) );
to
$mod_keys = trim( get_option( 'disallowed_keys' ) );
Reference:
https://github.com/takayukister/contact-form-7/issues/170